Articles Cookbook

Tag: Aggregate functions

How to Use Aggregate Functions in WHERE Clause

Filtering data according to the result of an aggregate function is a common data analysis task. So how do you use aggregates in the  WHERE clause? We’ll dedicate this whole article to answering that question.   Combining aggregate functions and filtering based on their results is often used in data analysis – e.g. showing branches with total sales above X,  countries where the number of posts is lower than Y, students with an average score below Z, and so on.

How to Combine Two Aggregate Functions in SQL

Having trouble using two aggregate functions in one query? This article will show you how to do it the right way – actually, the two right ways. In data analysis and reporting, we often need to count the number of records or sum them up and then calculate the average of this count or sum. Translated to SQL logic, this is the aggregation of aggregated data, or multi-level aggregation. For aggregation purposes, there are the SQL aggregate functions.

What Are Aggregate Functions in SQL, and How Do I Use Them?

Data is your source of knowledge. And thanks to SQL aggregate functions, you can extract the precise knowledge you need from your data efficiently. Read along to find out more. The core SQL aggregate functions are the following: COUNT(column_name | *) returns the number of rows in a table. SUM(column_name) returns the sum of the values of a numeric column. AVG(column_name) returns the average value of a numeric column.

An Overview of Aggregate Functions in SQL

Aggregate functions are commonly used in SQL. This article will lead you through their use and show examples of how they work. SQL aggregate functions are a useful tool, especially for creating reports. They’re not difficult to understand, especially if you have some experience with Excel or similar programs. You’ve probably used aggregate functions like SUM or AVERAGE in a spreadsheet. Even if you only occasionally use them, knowing aggregate functions can help you better understand your data and work more efficiently.

SQL Window Functions vs. SQL Aggregate Functions: Similarities and Differences

If you aren’t familiar with SQL’s window functions, you may wonder how they differ from aggregate functions. When should you use window functions? In this article, we’ll review window functions and aggregate functions, examine their similarities and differences, and see which one to choose depending on what you need to do. After you’ve tackled basic SQL, you’ll probably want to get into some of its more advanced functions. That’s great; these functions make reporting and analysis easier.

Common SQL Window Functions: Positional Functions

Positional SQL window functions deal with data's location in the set. In this post, we explain LEAD, LAG, and other positional functions. SQL window functions allow us to aggregate data while still using individual row values. We've already dealt with ranking functions and the use of partitions. In this post, we'll examine positional window functions, which are extremely helpful in reporting and summarizing data. Specifically, we'll look at LAG, LEAD, FIRST_VALUE and LAST_VALUE.

SQL Statistical Analysis Part 3: Measuring Spread of Distribution

Besides knowing the centers of a distribution in your data, you need to know how varied the observations are. In this article, we’ll explain how to find the spread of a distribution in SQL. Are you dealing with a very uniform or a very spread population? To really understand what the numbers are saying, you must know the answer to this question. In the second part of this series, we discussed how to calculate centers of distribution.

An Introduction to Using SQL Aggregate Functions with JOINs

Previously, we've discussed the use of SQL aggregate functions with the GROUP BY statement. Regular readers of the our blog will also remember our recent tutorial about JOINs. If you're a bit rusty on either subject, I encourage you to review them before continuing this article. That's because we will dig further into aggregate functions by pairing them with JOINs. This duo unleashes the full possibilities of SQL aggregate functions and allows us to perform computations on multiple tables in a single query.

A Beginner’s Guide to SQL Aggregate Functions

Aggregate functions are powerful SQL tools that compute numerical calculations on data, allowing the query to return summarized information about a given column or result set. These functions can be used in conjunction with the GROUP BY statement. Let’s see how they work using some easy examples. SQL Aggregate Functions Suppose we have users residing in a city, and we store their information in two tables. These tables and their relationship are shown below:

Useful SQL Patterns: Conditional Summarization with CASE

As you start coding in SQL, you will use some statements and techniques over and over again. We call these "SQL patterns". This series will look at the most common SQL patterns and consider how to use them. Previously, we looked at the SQL pattern of matching NULLs. This is important when you are comparing columns containing NULL values. Today, we're going to consider another SQL practice: conditional summarization with CASE operator.

NULL Values and the GROUP BY Clause

We've already covered how to use the GROUP BY clause and some aggregation functions like SUM(), AVG(), MAX(), MIN(), COUNT(). In this article, we will explain how the GROUP BY clause works when NULL values are involved. We will also explain about using NULLs with the ORDER BY clause. The best way to master GROUP BY and NULL in SQL is through practice. I recommend the SQL Practice track at LearnSQL.

Tag: Alias

How to Use Aliases with SQL JOINs

SQL aliases are custom names that you can give to the columns and tables you include in your queries. Aliases are very useful, as they can greatly improve the readability and maintainability of your query. We’ll be taking a closer look at using SQL aliases with JOIN and why you might need to do so. There are several types of aliases you can use in SQL: Aliases for tables.

Tag: Avg

The SQL AVG() Function Explained With Examples

We explain the SQL AVG() function with practical examples, covering how and where you can and cannot use it. The average is probably one of the most widely used metrics to describe some characteristics of a group. It is so versatile and useful that it can describe something about almost anything. If you like sports, you see things like average runs per game in baseball, average assists per game or per season in basketball, and so on.

The SQL Coalesce Function: Handling Null Values

You may already know how to return null values in SQL. Now, we’re going to learn how to do the opposite. Though the SQL COALESCE function may seem complex, it’s actually very straightforward and useful. Let’s look at several examples of how the SQL COALESCE function can be used to work with NULL values in SQL. The Need for Coalesce in SQL Before we dive into the SQL COALESCE function in detail, you should understand how NULL values behave in expressions.

How Often Employees Are Running Late for Work: SQL Datetime and Interval SQL Arithmetic

Computing Tardiness: Date, Time, and Interval SQL Arithmetic In this article, we’re going to discuss some interesting operations we can perform with date-related data types in SQL. The SQL standard, which most relational databases comply with these days, specifies the date-related data types that must be present in relational databases. The most important of such data types are date, time, timestamp, and interval. Here’s a brief rundown of the differences between these data types:

Tag: B2b offer

LearnSQL.com For Your Business

Are you thinking about SQL training for your employees? See how much you have to gain by choosing LearnSQL.com and how we can help you grow your business. .pre-header { color: #006DFF; text-transform: uppercase; letter-spacing: 2px; font-size: 14px; font-weight: 400; line-height: 16px; margin-top: 60px; } We live in a time when the ability to process data is crucial. Data is a key resource, the use of which can give you an edge in the market.

Tag: Behind the scenes

How to Set Up a Company SQL Training Program with LearnSQL.com

Are you looking to set up a business or corporate SQL training for your company's employees? In this article, we’ll discuss how to build an efficient SQL training program and why the LearnSQL.com platform is the choice of leading tech companies. If you are responsible for employees’ professional development – especially in a data-driven company – you know that SQL is essential for anyone who works with data. This programming language can enhance the performance of data and business analysts (for whom SQL is often a primary tool) as well as marketers, salespeople, HR specialists, auditors, and many more.

LearnSQL Track of the Season: SQL from A to Z

The ability to analyze data is one of the most sought-after skills in job applicants. Why? Because all organizations want to take advantage of the power of data. And one of the basic tools for that is SQL! See why we have chosen the SQL A to Z track as our track of the season. This fall, take your analytical skills to the next level! Let's start with the basics.

SQL Track of the Season: SQL Fundamentals in PostgreSQL

Are you ready for a new challenge this spring? Check out our SQL Track of the Season: SQL Fundamentals in PostgreSQL! In this article, we’ll answer common questions about this track. It’s getting warmer. The flowers are slowly beginning to bloom. This can mean only one thing – spring is here. The world is coming to life after its wintertime lethargy. This is a great time for new challenges. Do you want to add something to your skillset?

LearnSQL Track of the Season: Creating Database Structure

New year, new challenges, and ... a new SQL Track of the Season! Start 2021 by learning SQL and data engineering. In this article, we answer frequently asked questions about our Creating Database Structure track. Maybe you haven't noticed yet that there’s an order to many LearnSQL.com courses; you can learn SQL by doing them in the right order. We call this option our ‘SQL tracks’. These are logically structured and well-thought-out learning paths that will help you take the next steps towards becoming an SQL expert.

SQL Means Business - The Way of an Engineer

Have you been wondering why some companies fail and others achieve success? It's not a matter of luck but of the right people. Łukasz Kubicki at Vertabelo deals with business and product development. I asked him how he started his adventure with programming, how an engineer got into business, and if he liked playing computer games. Here's what he said. If you were to write one sentence about yourself, what would it be?

Did You Know LearnSQL.com Has Free SQL Courses?

Who doesn't like getting something for free? Each month, we give LearnSQL.com users a bit of help in their learning journey – a free, fully interactive SQL course. Since April, we have been giving our users the opportunity to learn SQL for free. Each month, we choose one of our SQL courses and give you full access to it for that month – completely free of charge! Cool, right?

Behind the Scenes at LearnSQL.com: How Our SQL Courses Are Created

Take a peek behind the scenes and learn our secret for creating great SQL courses! Have you ever wondered how LearnSQL.com courses are created? Are we looking at a lot of hard work or just a bit of magic? Or maybe both? Here’s a hint: we rely on proven methods to create user-friendly online courses. But it’s not easy! Read on to see the 8 steps we take when creating a new SQL course.

LearnSQL Track of the Season: SQL from A to Z

During Fall 2020, our main SQL track, SQL from A to Z, will be in the spotlight. In this article, we answer the most frequently asked questions about this track. At LearnSQL.com, our SQL courses are organized into tracks. A track is a sequence of courses designed to help you achieve a specific learning goal. The courses in the track are in a recommended order that progresses from the easiest to the most challenging.

A Mathematician in the World of SQL

She has a PhD in Mathematics and over 10 years’ experience teaching mathematics and computer science at the University of Warsaw. She knows SQL better than just about anyone I’ve met. Let’s get to know Agnieszka Kozubek-Krycuń, Vertabelo’s Chief Content Officer at Vertabelo. Let's go back in time. How did your adventure with math start? I’ve always enjoyed abstract concepts and problem solving. I was fascinated by variables when we learned to solve simple equations like x+2=5 in primary school.

You Want to Learn SQL? You've Come to the Right Place!

It is difficult to list all the benefits of learning SQL. You will work faster and more efficiently with a database, you will no longer be dependent on the IT department, and you will be able to analyze the data yourself and draw appropriate conclusions, among others. Add reporting to this, and you will get a very wide range of cool and useful skills. Maybe you want to change jobs or get a promotion?

Why Take the “SQL Basics” Course at LearnSQL.com

LearnSQL.com’s interactive “SQL Basics” course teaches the foundations of SQL. Discover why we built this online course, our philosophy behind it, and what it contains! What Is SQL, and Why Should You Learn It? SQL is a language used to talk to databases, computer programs that hold data and can process it efficiently. SQL can select data from a database and perform various computations on the data, be they simple or complex.

The Man Behind LearnSQL.com

If it wasn't for this guy, LearnSQL.com would never have been created. He manages the entire company, makes strategic decisions – and talks little about himself. Who is the man behind LearnSQL.com? Meet Vertabelo CEO Jarosław Błąd. SELECT interests, early_career, advice FROM Jarek AS the_man_behind_learnsql.com WHERE answer IS NOT Null AND success IS True; If you were to write one sentence about yourself, what would it be? I think I would say that I am an ordinary, simple guy who really likes what he does.

SQL Cookbook with Recipes for Success

The internet holds a lot of information and can provide solutions to various problems. SQL users, both beginners and advanced, often turn to the internet for help with SQL queries. This article will help you find the right SQL queries to solve your problems. Learn what the SQL Cookbook is and why you should use it. You will also find a list of the most important recipes, from which you will prepare a great SQL dish with the taste of success.

Tag: Bi

How to Get More from Your BI Tools with SQL

Are you frustrated with the limitations of your business analytics tool? Do you wonder if there are other features you could tap into? Would you like to know how SQL compliments your work with Power BI and Tableau? Read this article to learn more! If you are a data analyst or if data analysis is part of your everyday job, Business Intelligence (BI) tools are crucial for your work. You also know that most databases run SQL queries in the background of such tools.

Tag: Bigquery

An Overview of SQL Text Functions in Google BigQuery

Data analysts and Google BigQuery go hand in hand. Google's cloud data warehouse presents you with plenty of opportunities for using standard SQL text functions you can't avoid in your day-to-day work as a data analyst. BigQuery uses Google Standard SQL, an ANSI-compliant SQL dialect. This means you can use standard SQL text functions in BigQuery without needing to learn a variant of a given function. The Standard SQL Functions course is an excellent resource for learning those functions.

Tag: Birthday

2nd Anniversary of LearnSQL.com

It’s happening! Today we celebrate the 2nd anniversary of Learn SQL.com. We have come a long way together. Thank you for being with us and we promise to get even better every day! 731 days have passed since February 23, 2020, when we launched the LearnSQL.com platform. That's 17544 hours or 63158400 seconds if you prefer. It's been a long time, but it feels like yesterday that we started out together.

Anniversary of LearnSQL.com

Consider the period from Feb. 23, 2020 to Feb. 22, 2021. A year, 255 working days. Is that a lot of time? Well, it depends. For the LearnSQL.com Team, the time has passed blazingly fast. If someone had told us a year ago that we would be where we are now, we would have said, ‘We wish!’. We had a clear vision and a plan to create the most comprehensive SQL training platform in the world, with the best set of hands-on online SQL courses, and top-notch reading materials.

Tag: Book

The Best SQL Books for 2022

Many of our users keep asking what SQL books they should read to develop their skills. This is a great way to extend the knowledge you gained in online courses. Here are my picks for the SQL-related books you should read in 2022. It's January – a time of planning and New Year's resolutions. Put reading and learning SQL on your list. I've read many books on SQL. Some were great, while others were quite mediocre (to say the least).

Interviewing Data with Anthony DeBarros, Author of Practical SQL

Some make model ships, others collect stamps. I read SQL books. I've read a lot of them, but only a very few deserve to be called really good. Some of them were included in my last year's Six Favorite SQL Books list. The good news is that one of them just got a new release. It was great, even better than the previous edition! Moreover, I was able to talk to its author, Anthony DeBarros.

Read These 5 Data Analysis Books to Jump-Start Your Career

Do you want to pivot into a data analyst role, but you are unsure where to start? Do you do analytics in your job and would like to learn more about the big picture of data? Are you looking for a great data analysis book to read? In this article, you will find our selection of the best books on data analysis! If you are a business professional thinking about picking up data analytics skills, you may be wondering how you should start.

Which SQL Books Should You Read in 2021?

Readers keep asking for books that I can recommend to complement our SQL courses. There are quite a lot of SQL books on the market, but only a few are worth your attention. See which SQL-related books to read in 2021. A while ago, I wrote an article about my favorite SQL books for 2020. I chose books about various aspects of working with databases with the goal of helping you get a clear picture of SQL in the real world.

Our 6 Favorite SQL Books

So you want to learn SQL and query databases? Great! Check out these six SQL books for an in-depth look at the language and you’ll be writing queries in no time! You take SQL courses, participate in internet discussions and forums, watch tutorials on YouTube... What else can you do to develop your skills? Sometimes it’s good to reach for old-fashioned sources of knowledge: SQL books. Which book(s) should you choose?

Book Review: “Learn SQL the Hard Way” by Zed A. Shaw

“Learn SQL the Hard Way” by Zed A. Shaw is a great ebook for those who want to learn SQL essentials. At $19.99 USD, it may seem a bit expensive for an ebook, but you’re getting a DRM-free PDF, plus a whole bunch of explanatory videos and additional files. Who should read “Learn SQL the Hard Way”? Anyone interested in SQL basics – modifying databases or selecting information. Make no mistake about it: this book focuses heavily on the practical side of database language.

LearnSQL.com Review: “SQL Cookbook” by Anthony Molinaro

Recipes that make querying easy, even for the novice. In today’s information age, we have at our fingertips almost an overabundance of teaching and information on any and every subject. In the midst of this glut of information, it can be hard to decide which is the best source for our needs. But, fear not; we are here to assist you as you navigate through decisions about books on SQL topics!

5 Books That Will Grow Your SQL Skills

Which books will help you build your database skills? We look at five awesome SQL books. There’s a common saying that “all wise men read books”. I would say that all professionals read books – particularly those related to their field. There are many books about databases and SQL; most are tied to specific vendors (DB2, Oracle, MS SQL) but there are also plenty that are vendor-neutral. In this article, I’m going to review a few books that I would recommend to SQL learners at various levels of proficiency.

Can SQL Help Solve Crossword Puzzles?

Everyone has solved crossword puzzles and has certainly had some problems finding an appropriate word. Thanks to SQL, it is ridiculously simple to quickly dispel your crossword doubts and give you the correct answers. Of course, Google is commonly known as a universal cure for many doubts, but handling the problem yourself is much more rewarding. Recently I came across some simple and interesting examples from Andrew Cumming's book "

Tag: Books

The Best Books for Data Engineers

Are you tired of staring at a computer all day? Maybe it’s time to read a book. Take a moment to check out our list of recommended books for data engineers. They will help you deepen your knowledge about databases. Last year, we shared a list of the best books to learn SQL. This time, I want to introduce five books for data engineers. They are worth reading and will help you learn more about databases.

Tag: Calculating

SQL Statistical Analysis Part 2: Calculating Centers of Distribution

My previous article explained how to calculate frequencies using T-SQL queries. Frequencies are used to analyze the distribution of discrete variables. Today, we’ll continue learning about statistics and SQL. In particular, we’ll focus on calculating centers of distribution. We’ll learn e.g. how to calculate the SQL median, what functions to use to calculate the SQL mode, and how to calculate various types of mean in SQL (geometric mean, harmonic mean and, of course, arithmetic mean).

SQL Statistical Analysis Part 1: Calculating Frequencies and Histograms

Database and Business Intelligence (BI) developers create huge numbers of reports on a daily basis, and data analyses are an integral part of them. If you wonder whether you can perform statistical analysis in SQL, the answer is ‘yes’. Read my article to learn how to do this! Statistics are very useful as an initial stage of a more in-depth analysis, i.e. for data overview and data quality assessment. However, SQL statistical analysis possibilities are somewhat limited as there are not many statistical functions in SQL Server.

Tag: Career in data science

Why Use SQL Over Excel

SQL is replacing Excel in many fields, and data analysis is certainly one of them. If you are still using Excel as a data analyst, you are missing something very valuable. SQL can make your life easier, as it's more efficient and faster than Excel. So, how and from where can you learn SQL? How Can SQL Help Data Analyst? You can use SQL to help you with the following work:

Career Change: From Accountant to Database Designer

How do career changes and life choices impact our future? Can we change the path that's been set for us? And if so, where do we begin? I wouldn't blame you if you thought this article is about change. In a sense, it is—it's in the title, after all. But for me, this article is more about what remains constant. If somebody were to ask me what hasn't changed for me since my childhood, I would know the answer immediately: curiosity.

Complete SQL Practice for Interviews

Congratulations! Your SQL skills were strong enough to get you that job interview! Now, if you only knew what SQL questions and practical exercises a recruiter might ask you to do… This article is meant as a SQL practice for interviews. I’ll help you prepare for the SQL and database aspects of your job interview. In a previous article, I explained how can you boost your career by learning SQL.

Finding the Perfect SQL Job

So you have some SQL skills and you're looking for a job that will use them. What are your options? SQL is everywhere, and there's a huge demand for people with database management skills. This is especially the case when companies start implementing Big Data solutions and strategies. There's no arguing that SQL is a must-have skill. If you're already proficient, how can you put your expertise to practical use in the job market?

A Day in the Life of a SQL Developer

What is a SQL developer? And what does a SQL developer do? Describing a “typical” day for a SQL developer is not easy. When your daily work is using various technologies to create interesting database-oriented products, very few days are alike! Each day brings a new and intriguing challenge. Nevertheless, I’ll have a go at explaining what everyday things a SQL developer might do. Morning: Arrive at Work What does a SQL developer do after arriving at the office?

Tag: Case

How to Use CASE in ORDER BY in SQL

This article will show you how and when to use CASE in an ORDER BY clause. Have you ever used a CASE statement? I’m sure you have, at least in a SELECT statement. But have you ever used it in an ORDER BY clause? No? You will, once I show you how! Don’t worry if you’ve never used a CASE statement. I’ll show and explain it to you with a short example.

How to Use CASE in SQL

If you need to evaluate multiple conditional statements, the SQL CASE statement will do the job. Here’s what you need to know to use CASE like a pro. Why is CASE so important in SQL? If you’re analyzing or manipulating data, you’ll often want to define rules based on certain conditions, e.g. if an employee’s performance is above average, give them a 10% raise; if it is outstanding, give them a 15% raise; otherwise, give them a 5% raise.

Useful SQL Patterns: Conditional Summarization with CASE

As you start coding in SQL, you will use some statements and techniques over and over again. We call these "SQL patterns". This series will look at the most common SQL patterns and consider how to use them. Previously, we looked at the SQL pattern of matching NULLs. This is important when you are comparing columns containing NULL values. Today, we're going to consider another SQL practice: conditional summarization with CASE operator.

Using CASE with Data Modifying Statements

What happens when you combine CASE with SQL's data modifying statements? Find out in this article. The CASE expression is a very useful part of SQL and one that you'll employ frequently. We've already covered what the CASE expression does, how to format it, and how to use it in a SELECT statement in "Using CASE to Add Logic to a SELECT". Another article, "How to Sort Records with the ORDER BY Clause"

Using CASE to Add Logic to a SELECT

As you write an SQL query, you may need to get values from multiple columns and change values from one form to another. The simple way to achieve this goal is to add a CASE expression to your SELECT statement. In this article, we'll introduce you to the syntax, formats, and uses of the CASE expression. The CASE expression is a conditional expression: it evaluates data and returns a result.

Tag: Case when

What Is CASE in SQL?

SQL CASE is a very useful expression that provides if-else logic to your SQL queries. It’s a slightly more advanced topic, but you’ll need it when preparing reports – it will deliver massive value to your personal and professional projects. The SQL CASE statement is a control flow tool that allows you to add if-else logic to a query. Generally speaking, you can use the CASE statement anywhere that allows a valid expression – e.

Tag: Cheat sheet

Standard SQL Functions Cheat Sheet

Download this 2-page Standard SQL Functions Cheat Sheet in the PDF or PNG format, print it out, and put it up on a wall or keep it on your desk. The Standard SQL Functions Cheat Sheet provides you with the syntax for different text and numeric functions, CASE WHEN, NULLs, date and time types, INTERVALs, and aggregate functions. The Standard SQL Functions Cheat Sheet has a handy troubleshooting section and plenty of examples.

SQL Basics Cheat Sheet

Download this 2-page SQL Basics Cheat Sheet in PDF or PNG format, print it out, and stick to your desk. The SQL Basics Cheat Sheet provides you with the syntax of all basics clauses, shows you how to write different conditions, and has examples. You can download this cheat sheet as follows: Download 2-page SQL Basics Cheat Sheet in PDF format (A4) Download 2-page SQL Basics Cheat Sheet in PDF format (Letter) Download 1-page SQL Basics Cheat Sheet in PDF format (A3) Download 1-page SQL Basics Cheat Sheet in PDF format (Ledger) You may also read the contents here:

SQL JOIN Cheat Sheet

Download this 2-page SQL JOIN Cheat Sheet in PDF or PNG format, print it out, and stick to your desk. The SQL JOIN Cheat Sheet provides you with the syntax of different JOINs, and examples. You can download this cheat sheet as follows: Download 2-page SQL JOIN Cheat Sheet in PDF format (A4) Download 2-page SQL JOIN Cheat Sheet in PDF format (Letter) Download 1-page SQL JOIN Cheat Sheet in PDF format (A3) Download 1-page SQL JOIN Cheat Sheet in PDF format (Ledger) SQL JOINs Cheat Sheet JOINING TABLES JOIN combines data from two tables.

SQL Window Functions Cheat Sheet

Download this 2-page SQL Window Functions Cheat Sheet in PDF or PNG format, print it out, and stick to your desk. The SQL Window Functions Cheat Sheet provides you with the syntax of window functions, a list of window functions, and examples. You can download this cheat sheet as follows: Download 2-page SQL Window Functions Cheat Sheet in PDF format (A4) Download 2-page SQL Window Functions Cheat Sheet in PDF format (Letter) Download 1-page SQL Window Functions Cheat Sheet in PDF format (A3) Download 1-page SQL Window Functions Cheat Sheet in PDF format (Ledger) Window Functions Window functions compute their result based on a sliding window frame, a set of rows that are somehow related to the current row.

Tag: Coalesce

How to Use the COALESCE() Function in SQL

SQL users are often faced with NULL values in their queries and need to process them properly. The COALESCE() function helps handle NULL values. Read this article to learn how to use COALESCE() in your queries. SQL tables store data in records, and records are composed of fields. There can be situations where we don’t know the value for a specific field. For example, let’s suppose we have a table with data for persons.

Tag: Codds article

51 Years of Relational Databases

If it weren't for him, there would be no modern databases. It is the 51st anniversary of the publication of his article that changed the rules of the game. Edgar Frank Codd is one of the fathers of SQL, and his name is one of the first to be mentioned in the history of databases. Or maybe even the history of computer development in general? See what we owe to Dr.

Tag: Common sql functions

18 Useful Important SQL Functions to Learn ASAP

Beginning with SQL: Useful Functions to Master Learning a new programming language can seem intimidating. Like any other language, a programming language has a large vocabulary that you need to master. In this article, we'll look at some of the most useful SQL functions that you need to know. There are many useful SQL functions for working with different data types. Once you practice with some of the most common ones, you'll gain enough confidence to move on to more advanced material.

Tag: Common sql mistakes

Extracting Data From a String: SPLIT_PART in PostgreSQL

Learn how to use split_part in PostgreSQL to extract data from strings. Quite often, we’d like to extract parts of a string when working with text values. A common example is when we have a full name and need to retrieve only the last name. In this article, we’ll examine how to do it using split_part in PostgreSQL, i.e. a string-related function that can be used to extract a substring.

How to Remove Junk Characters in SQL

Unwanted characters in text data can be a bit of a pain, but there’s an easy way to fix them. Scroll down to learn how to remove junk characters in SQL in the easiest way! Sometimes, we’ll find unwanted characters inside our string data because our SQL queries didn’t work as expected. Moreover, these extra characters may sometimes be invisible, which really complicates things. In this article, we’ll examine some string-related SQL functions that can handle unwanted characters—visible or not!

How to Solve Capitalization Data Quality Issues

Misspelled names, typos, and text data quality issues in your database? Power up your queries! Use SQL string functions to address data quality issues related to capitalization. Sometimes, our SQL queries don't work as expected because of data quality issues. In this article, we will examine some string-related SQL functions that can correct data quality issues related to capitalization. We'll be using PostgreSQL in our examples, but similar functions are available in most database engines.

Preventing Common SQL Mistakes

Regardless of the engine you are using (SQL Server, MySQL, Oracle, etc.), you can prevent common errors and simplify the debugging process. This article will discuss some of the common SQL mistakes you’ll face and will help you correct them easily. One of the best ways to prevent the most common SQL mistakes is to keep your queries clear and readable. It’s very easy to forget the ideas behind your code!

Tag: Common table expressions

SQL CTE Explained

In this article, you will learn about SQL Common Table Expressions (CTEs). This powerful SQL tool will help you simplify complex queries. Additionally, I will introduce you to the two main types of CTEs and some of their use cases.  CTE Primer The Common Table Expression (CTE) was introduced to standard SQL to simplify long, complex queries (especially joins and subqueries). It is a temporary data set returned by a query that contains data separate from the main query.

How to Draw a Christmas Tree in SQL

You can use SQL to manipulate all kinds of data, from huge analytical queries to brief single-purpose statements. But you can also use SQL just for fun, without any business requirements stifling your creativity. So, get out your jolly hat and prepare to sing O Christmas Tree as we create some quirky art with plain old SQL. Today, we’re going to generate some holiday-themed ASCII art, just for fun. That’s right.

Simplify SQL Code: Recursive Queries in DBMS

Hey SQL users! Are you repeating the same query in every report? Are your queries getting too complicated? Use recursive queries to simplify SQL code! Too many SQL reports can lead to clutter on your desktop and in your head. And is it really necessary to code each of them separately? Ad-hoc queries can share much of the same SQL code with managerial reports and even regulatory reports. Suppose you’ve been writing basic SQL code for a while.

How to Organize SQL Queries with CTEs

Common table expressions (CTEs) allow you to structure and organize SQL queries. Knowing how to organize SQL queries is a necessity when you begin to move deeper into SQL, so if you want to become an SQL master, you need to know CTEs. The SQL CTE has been part of standard SQL for some time now. CTEs – which are also called WITH statements – are available in all major RDBMS.

Long SQL Query vs. Recursive SQL Query

Recursion is one of the central ideas in computer science. We can define it as a method for solving problems where the solution of the problem depends on solving a smaller instance of a problem. If this sounds complicated do not fret, in this article we will learn about recursion in SQL that you can practice and deepen in Vertabelo Academy. Recursion is a way of solving hierarchical problems we find in data with common SQL.

Tag: Conditional summarization

Useful SQL Patterns: Conditional Summarization with CASE

As you start coding in SQL, you will use some statements and techniques over and over again. We call these "SQL patterns". This series will look at the most common SQL patterns and consider how to use them. Previously, we looked at the SQL pattern of matching NULLs. This is important when you are comparing columns containing NULL values. Today, we're going to consider another SQL practice: conditional summarization with CASE operator.

Tag: Constraints

What Is a NOT NULL Constraint in SQL?

SQL has several ways of dealing with NULLs. In this article, we’ll focus on the NOT NULL constraint and other NULL-related clauses. Understand this and you’ll take an important step in your SQL growth! Before we get straight into the NOT NULL constraint, let’s quickly define what NULLs and constraints are. NULL values are a central concept in SQL databases. The idea behind a NULL value is simple: a NULL value means that we do not have a known value for that field.

Tag: Count

The SQL Count Function Explained With 7 Examples

One of the most useful aggregate functions in SQL is the COUNT() function. If you are new to SQL and want to learn about the various ways to use the COUNT() function with some practical examples, this article is for you. The COUNT() function is one of the most useful aggregate functions in SQL. Counting the total number of orders by a customer in the last few days, the number of unique visitors who bought a museum ticket, or the number of employees in a department, can all be done using the COUNT() function.

Tag: Course of the month

Free SQL Course of the Month – Window Functions in PostgreSQL

Are you looking for the best way to master SQL window functions? In this article, I'll show you how you can do so for free. Throughout August 2022, you can access the interactive course Window Functions in PostgreSQL for free. Hurry, time is running out! Need a free PostgreSQL course on window functions? You've come to the right place! If you are reading this article, you probably know PostgreSQL is one of the most popular databases in the world.

Free Course of the Month – Writing User-Defined Functions in PostgreSQL

Why learn to write user-defined functions? I’ll explain in this article – and how you can learn for free during July 2022 with this LearnSQL.com  PostgreSQL course! PostgreSQL is one of the most popular databases in the world. This is mainly due to its great functionality and the fact that it’s open source (i.e. free!). Postgres is fast, it runs on multiple systems, and it’s suitable for almost any application.

SQL Track of the Season: SQL from A to Z in MySQL

Do you feel the spring already? Everything is in full bloom at this time of the year. Why shouldn’t it be the same with your career? You just need to water it with a new skill. Here is the brilliant SQL from A to Z in MySQL track, our Track of the Season. In this article, I answer common questions about this awesome set of online MySQL courses. Why should you care about relational databases at all?

Free Course of the Month – GROUP BY Extensions in PostgreSQL

Do you work with data? Want to be able to create better and more sophisticated SQL reports? Then check out our interactive GROUP BY Extensions in PostgreSQL course. In April 2022, you can complete this online PostgreSQL course for FREE! How can you get this free SQL course in April? Create a free com account or log in if you already have one. Start the course. You will have free access to its content until the end of the month.

Free SQL Course of the Month – Creating Basic SQL Reports in PostgreSQL

If you are looking for a course that takes your PostgreSQL skills to a completely different level, you've come to the right place. You can learn for free in March! We chose SQL Reporting in PostgreSQL for our Free SQL Course of the Month. It's just awesome – I'll tell you why. Do you want to be even better at SQL? Do you know the basics and want your SQL reports to be even more sophisticated?

Free Course of the Month – PostgreSQL JOINs

Our PostgreSQL JOINs course will help you consolidate your knowledge of working with data from two or more tables in a PostgreSQL database. Throughout the month of January, this awesome SQL course is absolutely FREE! Wondering why we want to give you this SQL course for free? We've been doing this for a long time. Every month, we choose one of our interactive online SQL courses and give users free access to it.

Free Course of the Month – Common Functions in PostgreSQL

Do you want to be able to use popular PostgreSQL functions and process different types of data more easily? You've come to the right place! Here is the Common Functions in PostgreSQL course. Throughout the month of December, this SQL course is absolutely FREE! You are probably wondering: why is LearnSQL.com offering a free SQL course? Well, we've been doing this for a long time. We choose one of our courses every month and give users free access to it.

Free SQL Course of the Month – Window Functions in PostgreSQL

This is what distinguishes ordinary SQL users from professionals – SQL window functions! Would you like to practice them in PostgreSQL, on one of the best interactive SQL courses in the world, and pay nothing for it? Throughout November, you have access to the Window Functions in PostgreSQL course for FREE. You read it right: you won't pay a penny! What's the catch? Why would someone give you a free course?

Free Course of The Month – SQL Practice Set in MS SQL Server

You have to train a lot to learn a new skill. It is the same with MS SQL Server. Do you want to write good SQL queries? Or maybe you are preparing for a job interview? You've come to the right place! Throughout October you will have access to our amazing hands-on MS SQL Server course for FREE! You probably just thought: “There must be a catch. Why would someone give away SQL courses for free?

Free Course of The Month – Revenue Trend Analysis in SQL Server

It is impossible to run a business without a good analysis of revenue trends. But how do you do it effectively? You can rely on good old Excel, but a much better idea is to use SQL and databases. Learn how to create SQL reports and track the growth of your business with MS SQL Server. Here is the course, Revenue Trend Analysis in SQL Server. It’s FREE throughout September!

Free SQL Course of the Month – Creating Basic SQL Reports in SQL Server

This is another in our series of free SQL Courses of the Month. This time, you can learn SQL Reporting in MS SQL Server for free. Do you want to be able to prepare even better SQL reports? Or maybe you have some basic knowledge of SQL Server (one of the major SQL dialects) and would like to go a step further? This is the course for you.

Free Course of the Month – GROUP BY Extensions in MS SQL Server

Do you create SQL reports? Do you want them to be even better and more effective? Are you working with MS SQL Server and want to expand your query writing skills? Here is a great, interactive GROUP BY Extensions in MS SQL Server course. For the month of June, you can learn and finish this course for absolutely free. How can you get this free SQL course in June?

SQL Course of the Month – SQL Practice Set

Are you starting your adventure with SQL and looking for a place to practice your SQL queries? Or maybe you are preparing for a job interview? I have good news for you. Throughout May, you will have access to our amazing SQL practice course for FREE! Why is LearnSQL.com giving you a free SQL course? Every month, our users get the opportunity to take one of our great SQL courses for free.

Free SQL Course of the Month – Creating Basic SQL Reports

Do you want to create good SQL reports from scratch? Are you looking for a course that will help you spread your analytical wings? What if I told you that throughout April 2021, you could access one of the best SQL Reports courses for FREE? Here it is: Creating Basic SQL Reports. What's the catch? There is none. LearnSQL.com provides one of their courses for free from time to time.

Free SQL Course of the Month – Window Functions

Are you looking for a good SQL window functions course? What if I told you that throughout March, you could access the best window functions course in the world for absolutely FREE? You read that right: you won't pay a dime! Hurry up! Time is running out! But wait – why is LearnSQL.com giving you a free SQL course? Well, we believe sometimes you just have to be good to others.

SQL Course of the Month – SQL JOINs

If you want to really learn SQL, you can’t skip SQL JOINs. They are some of the most fundamental and commonly used features of the SQL language. That’s why SQL JOINs is our February SQL Course of the Month. What makes SQL JOINs so important? I asked Agnieszka Kozubek-Krycuń, Vertabelo's Chief Content Officer, about it. Here's what she said. Is it true that SQL JOINs are one of the foundations of SQL?

SQL Course of the Month – Standard SQL Functions

Are you dreaming of becoming a data analyst? Or maybe you just want to work effectively with your company’s databases? You can – with SQL functions. We’ve selected Standard SQL Functions to be our January 2021 SQL Course of the Month. What will you find inside? I asked Agnieszka Kozubek-Krycuń, Vertabelo's Chief Content Officer, about it. Here's what she said. What are SQL functions? The term reminds me of SELECT or JOIN.

SQL Course of the Month – Customer Behavior Analysis in SQL

Do you run a business? Do you want to squeeze even more out of your data? Start by analyzing your customers' behavior using SQL! Throughout December, you can learn how to do it for free on LearnSQL.com! I asked Agnieszka Kozubek-Krycuń, Vertabelo's Chief Content Officer, about our December Course of the Month, Customer Behavior Analysis in SQL. Here's what she told me. Let's start with the basics: Why analyze customer behavior?

SQL Course of the Month – GROUP BY Extensions in SQL

Do you want to develop your SQL skills? Do you want to get more out of your data and prepare better reports and summaries? The answer is learning to use SQL’s GROUP BY extensions. But how should you go about this? I asked the same question to Agnieszka Kozubek-Krycuń, Vertabelo’s Chief Content Officer. As she explains, the secret is in this November’s free SQL Course of the Month: GROUP BY Extensions in SQL.

SQL Course of the Month – How to INSERT, UPDATE, and DELETE Data in SQL

So, you've started learning SQL, and you already know what the SELECT command is and when to use it! Congratulations! Now, it's time to take the next step towards becoming an expert. You need to know the SQL UPDATE, INSERT, and DELETE commands to modify data in your tables. These are the basics that will allow you to work with tables. But what's the best way to learn them? I asked Agnieszka Kozubek-Krycuń, Chief Content Officer at Vertabelo.

SQL Course of the Month – Analyzing Revenue Trends in SQL

We work hard, we learn SQL, and we develop professionally. But why? For our own satisfaction, but also for money! The knowledge of SQL will increase your income significantly. If you are proficient in SQL, you can better analyze your company's revenue. How? I asked Agnieszka Kozubek-Krycuń, Chief Content Officer at Vertabelo. In this article, she answers your questions about our September SQL Course of the Month: Analyzing Revenue Trends in SQL.

SQL Course of the Month – Recursive Queries

Recursive Queries is one of SQL’s more advanced features. You could say they divide SQL users into beginners and experts. But how do you learn recursive queries? And why do you need them, anyway? Agnieszka Kozubek-Krycuń, Chief Content Officer at Vertabelo, is here to help. In this article, she answers your questions about our August SQL Course of the Month: Recursive Queries. Recursive queries … that sounds very serious.

SQL Course of the Month – PostGIS

It's summer, and it's travel time ... at least it would be under normal conditions. The pandemic is still going on, but that doesn't stop us from dreaming about distant trips and visits to beautiful places. For now, most of us will have to do it on a map. Did you know that databases can store geographical data? With interactive maps, if you find a nice summer house on the internet, you can accurately track it and plan the best route there.

SQL Course of the Month – SQL Practice Set

It is said that practice makes perfect. I agree with this statement one hundred percent. What is applicable in basketball training, playing an instrument, or learning a foreign language is also useful in learning SQL. Practicing writing queries, using functions, and putting together clauses is the basis for learning the true power of SQL. But how and where do you practice SQL? I spoke with Agnieszka Kozubek-Krycuń, Chief Content Officer at Vertabelo about this.

SQL Course of the Month – Creating Basic SQL Reports

In May, we chose Creating Basic SQL Reports as our course of the month. Why? Because the basis of every successful business is making the right decisions based on proven data and good SQL reports. I asked Agnieszka Kozubek-Krycuń, Chief Content Officer at Vertabelo, about this. She knows SQL better than just about anyone and is probably the best person to talk about SQL Reporting. What does it mean to create SQL reports?

SQL Course of the Month – Window Functions

Spring has come. It is nicer outside. It's a great time to learn something new. Which course should you choose? In April, it's worth it to bet on SQL window functions. What are they, what are they used for, and why are they worth knowing? I asked Agnieszka Kozubek-Krycuń, Chief Content Officer at Vertabelo, these questions. She has a PhD in mathematics and over 10 years’ experience teaching mathematics and computer science at the University of Warsaw.

Tag: Creating tables

Learn SQL Views in 30 Minutes

Views aren't complicated – if you've got half an hour, we'll get you started writing SQL queries using views! Let's start by answering the question "What is a view in SQL?'. A view is a database object (as is a table, an index, or a stored procedure). Like a table, you can query a view and extract the information in it. It can be used in the FROM clause of a SELECT, and you can reference view columns in clauses like SELECT, WHERE and GROUP BY among other clauses as well.

Tag: Csv

How to Import a CSV File to a MySQL Database

CSV files store and transfer data between databases. Read on to find out how easy it is to work with CSV files in a MySQL database. CSV files are one of the oldest data exchange formats and are still heavily used by IT professionals from various domains. It is common for online data resources and different database software to offer their data uploads and downloads in CSV format. In this article, we’ll briefly review what a CSV file is and how to work with it.

How to Export a CSV File From a T-SQL Query

Knowing SQL queries to select data from databases allows you to obtain information easily. However, there are many situations in which we need to export data to another platform or application. The CSV file is a solution to this problem. If you'd like to master complete SQL, try out our interactive SQL from A to Z track. It contains 7 hands-on SQL courses that will take you from a beginner to an advanced SQL user.

Tag: Cte

How to Write Multiple CTEs in SQL

Leverage the full potential of the CTE by combining two or more of them in a single SQL query. Common table expressions, or CTEs, can be a powerful SQL tool. When you write two (or even more) CTEs together, this power multiplies. In this article, I’ll show you three ways of writing multiple CTEs: Using two independent CTEs in one SQL query. Using two CTEs where the second CTE refers to the first.

How to Query a Parent-Child Tree in SQL

What are parent-child tree structures in SQL? In this article, we answer that question, talk about query hierarchy, and demonstrate the five most common SQL queries you’ll need for these data structures. Yes, you can use SQL on a parent-child tree structure. I’ll show you how in this article. Along the way, I’ll walk you through five query examples, starting with the easiest and ending with the most complex.

What Is a Common Table Expression (CTE) in SQL?

The common table expression (CTE) is a powerful construct in SQL that helps simplify a query. CTEs work as virtual tables (with records and columns), created during the execution of a query, used by the query, and eliminated after query execution. CTEs often act as a bridge to transform the data in source tables to the format expected by the query. A common table expression, or CTE, is a temporary named result set created from a simple SELECT statement that can be used in a subsequent SELECT statement.

Top 5 SQL CTE Interview Questions

Here are five questions (and solutions!) on CTEs you’ll (probably) be asked at an interview. I’m not saying you will get these SQL CTE interview questions at every job interview. But when you do, they are probably along the lines of the five I’m about to show here. Other than theoretical questions about CTEs, there are not that many variations in the CTE scenarios evaluated by interviewers. Go through these five examples, and you get a good foundation for acing your interview!

What Is a Recursive CTE in SQL?

The article that’ll show you practical examples of using recursive CTEs in SQL. If you’ve heard about SQL’s recursive CTEs but never used them, this article is for you. It’s also for you if you never get tired of recursive CTE examples. Before we dig into recursion, I’ll remind you what CTEs are and what their syntax is. Then I’ll do the same for recursive CTEs. After that, I’ll show you how recursive CTEs work in three examples.

The 7 Best Articles about the SQL Recursive Query

Do you want to learn about recursive queries but don’t know where to start? Here’s our selection of seven articles that should help you with diving into the recursive queries world. I won’t lie to you. Learning and understanding recursive queries can be difficult. But difficult things are usually worth trying. And by learning recursive queries, you’re making sure you know how to work with this very powerful tool.

3 Real-Life Business Questions That Are Perfect for SQL Common Table Expressions

We answer three SQL business questions using CTEs. There are business problems that are often solved in a very roundabout way. While they might get you the correct result, there’s usually a more elegant way to write a solution. Enter the CTEs! They are extremely helpful when it comes to getting a more direct and elegant solution. I’ll show you three business situations where CTEs can be very helpful. You’ll get an idea of when CTEs can be useful.

5 Practical SQL CTE Examples

Common table expressions (CTEs) were introduced into SQL to improve the readability and the structure of SQL queries, especially those requiring multiple steps to get the necessary output. In this article, we will go through several examples to show how SQL CTEs can help you with complex calculations and hierarchical data structures. Common Table Expressions in SQL Common table expressions (CTEs), also called WITH clauses, allow creating named subqueries that are further referenced in the main query.

5 Reasons Why You Should Use CTEs Instead of Subqueries

Common Table Expressions, or CTEs, were introduced in SQL:1999 to handle cases where the output of one query is used within another query. But didn’t we already have subqueries for this? In this article, I’ll demonstrate with multiple examples why CTEs are better than subqueries for the structure and readability of your SQL queries. Let’s start by reminding ourselves what CTEs and subqueries are and how they differ. Common Table Expressions vs.

What Is Advanced SQL?

Are you confused about advanced SQL skills? What are they? This article will explain what advanced SQL can mean, especially as we use it on LearnSQL.com. I’m sure you find the phrases ‘advanced SQL skills’ or ‘advanced SQL topics’ very often. You read one article about advanced SQL and you’re happy with how easy these advanced topics seem to be. Then you talk to someone and you see they consider everything you know as basic SQL knowledge.

A Guide to SQL Common Table Expressions

Common table expressions are a relatively new SQL feature that is sometimes overlooked by experienced practitioners working with relational databases. Don’t be one of them! Learn how to use SQL CTEs and join the many data analysts enjoying the benefits of this great tool. Common table expressions (CTEs), also known as WITH clauses, are used to create named subqueries that can be referenced in the main query. CTEs are not saved for future use and can be referenced only within the query where they are defined.

SQL CTE Explained

In this article, you will learn about SQL Common Table Expressions (CTEs). This powerful SQL tool will help you simplify complex queries. Additionally, I will introduce you to the two main types of CTEs and some of their use cases.  CTE Primer The Common Table Expression (CTE) was introduced to standard SQL to simplify long, complex queries (especially joins and subqueries). It is a temporary data set returned by a query that contains data separate from the main query.

Why the SQL WITH Clause Is Awesome

If you’re not using WITH clauses yet, it’s definitely time to start! SQL WITH clauses, or common table expressions, help improve the structure of SQL queries by making them more readable. That’s already a lot, but WITH clauses have many more benefits. Let’s see together! The WITH clause was introduced in SQL:1999 to define views that are only valid for the query they belong to. Also known as common table expressions (CTEs), WITH clauses allow us to improve the structure of an SQL statement without polluting the database namespace.

How to Get Descendants of a Parent in SQL

Want to learn how to handle family trees and find descendants of a parent? By reading this article, you’ll learn how to handle hierarchical data. Finding descendants from a parent is a common problem in SQL. If you imagine a family tree, the basic building block that forms the relationships within it is the parent-child relationship. The parent-child relationship is precisely what defines all hierarchical data. Another example of hierarchical data is the manager-employee relationship.

Where Can I Find Good SQL CTE Exercises?

Find the top online resources for SQL Common Table Expression (CTE) exercises! CTEs allow you to structure and organize SQL queries efficiently, which is essential if you want to advance your SQL knowledge. A Common Table Expression, or CTE, is a SQL syntax that creates a temporary data set. This set contains separate data than the main query, which can typically be referenced or reused in a subsequent query. A CTE is considered temporary because the result is not permanently stored anywhere and only exists for the duration of the query.

What’s the Difference Between SQL CTEs and Views?

SQL views vs. CTEs: What do they do? How are they different? Which one should you use and when? Get your answers here! In SQL, both CTEs (common table expressions) and views help organize your queries, leading to cleaner and easier-to-follow code. However, there are some important differences between them. This article will walk you through several examples of CTEs and views and explain when to use each one.

What are SQL CTE Best Practices?

Are you wondering what the best practices for using common table expressions are? This article will help you learn when to use a CTE and how to write it. If you have heard about SQL CTEs, you have probably noticed they’re often mentioned together with subqueries. Sometimes, people think there’s no difference compared to the subqueries, and there’s often debate about whether a CTE or subquery should be used to get a particular result.

How to Learn SQL Common Table Expressions (CTEs)

Common table expressions are very useful for organizing, traversing, and improving the readability of long SQL queries.  Moreover, recursive CTEs, which can reference themselves, solve problems that cannot be addressed with other queries. But how do you master common table expressions in SQL? In this article, I discuss the most effective strategies for learning CTEs and suggest how to address the common challenges of learning common table expressions on your own.

How to Use 2 CTEs in a Single SQL Query

Have you ever wondered how to use multiple CTEs in one SQL query? Read this article and find out about recursive CTEs. After learning common table expressions or CTEs, a natural question is “Can I use several CTEs in one query?” Yes, you can! And you can do it quite easily, especially if you already have some basic knowledge of CTEs. Whether you know a bit about CTEs or you’re entirely new to the CTE world, reading about what a CTE is is always a good start.

How CTEs Work

The SQL language offers a feature named Common Table Expressions, or CTEs. Also known as WITH clauses, CTEs are a fairly new addition to SQL. They help you break longer queries into smaller chunks, making your queries much easier to understand. Read the article to find out how to use CTEs and how they differ from traditional subqueries. Common Table Expressions (CTEs), which are essentially named subqueries, were first mentioned in the SQL standard between 1999 and 2000.

SQL CTEs Explained with Examples

Learn how you can leverage the power of Common Table Expressions (CTEs) to improve the organization and readability of your SQL queries. The commonly used abbreviation CTE stands for Common Table Expression. To learn about SQL Common Table Expressions through practice, I recommend the interactive Recursive Queries course at LearnSQL.com. It contains over 100 hands-on exercises on simple and complex recursive CTEs. What does a CTE do? Why might you want to use one in your SQL code?

When Should I Use a Common Table Expression (CTE)?

Interested in hearing more about common table expressions or CTEs? Would you like to know when CTEs are useful? Read on—we’ll discuss in this article. If you’ve heard of common table expressions, you’ve probably wondered what they do. Even if you have not, it’s good that you’re here! CTEs can be very useful, especially if you have already mastered the basics of SQL, such as selecting, ordering, filtering data, and joining tables.

What Is a CTE?

After mastering statements like SELECT, DELETE, INSERT, and GROUP BY, you might search for ways to improve code maintainability, reproducibility, and readability. At that point, you will probably start learning about modern SQL concepts that were introduced in the early 2000s. One such SQL technique is the CTE? (common table expression) —?a temporary named result set. In this article, you will learn what a CTE is and how to use it to improve the maintenance and the readability of your code.

How to Draw a Christmas Tree in SQL

You can use SQL to manipulate all kinds of data, from huge analytical queries to brief single-purpose statements. But you can also use SQL just for fun, without any business requirements stifling your creativity. So, get out your jolly hat and prepare to sing O Christmas Tree as we create some quirky art with plain old SQL. Today, we’re going to generate some holiday-themed ASCII art, just for fun. That’s right.

Simplify SQL Code: Recursive Queries in DBMS

Hey SQL users! Are you repeating the same query in every report? Are your queries getting too complicated? Use recursive queries to simplify SQL code! Too many SQL reports can lead to clutter on your desktop and in your head. And is it really necessary to code each of them separately? Ad-hoc queries can share much of the same SQL code with managerial reports and even regulatory reports. Suppose you’ve been writing basic SQL code for a while.

How to Organize SQL Queries with CTEs

Common table expressions (CTEs) allow you to structure and organize SQL queries. Knowing how to organize SQL queries is a necessity when you begin to move deeper into SQL, so if you want to become an SQL master, you need to know CTEs. The SQL CTE has been part of standard SQL for some time now. CTEs – which are also called WITH statements – are available in all major RDBMS.

Long SQL Query vs. Recursive SQL Query

Recursion is one of the central ideas in computer science. We can define it as a method for solving problems where the solution of the problem depends on solving a smaller instance of a problem. If this sounds complicated do not fret, in this article we will learn about recursion in SQL that you can practice and deepen in Vertabelo Academy. Recursion is a way of solving hierarchical problems we find in data with common SQL.

How Recursive Common Table Expressions Work

Recursive Common Table Expressions are immensely useful when you're querying hierarchical data. Let's explore what makes them work. Common Table Expressions (CTEs) are some of the most useful constructions in SQL. Their main purpose is improving query design, which makes queries easier to read. One of the reasons CTEs are so popular is that they let you divide longer queries into shorter subqueries. These are easier to read and edit.

How to Organize SQL Queries When They Get Long

The first long SQL query you’ll have to deal with is likely to be hard for you to structure and understand. These five tips will teach you the best way to organize SQL queries, i.e. write and format them. As we all know, SQL queries are essential to database management. Without them, it would be extremely difficult to find and work with the information in a database. Query length depends on the type of information we need and the size of the database.

Improving Query Readability with Common Table Expressions

What is a Common Table Expression, or CTE? Where do you use them, and why? This post answers your questions. Simply put, Common Table Expressions (also known as WITH clauses) are essentially named subqueries. They also provide additional features like recursion. If you're new to subqueries, I recommend you read the SQL Subqueries article before continuing. The main purpose of Common Table Expressions is to improve the design and readability of an SQL statement.

Tag: Data analysis

Roadmap to Becoming a Data Analyst

What is a data analyst? What are their daily duties, and what skills do they need? In this article, I discuss the role of data analysts and share a step-by-step guide on how to become one. As organizations start to realize the value of their data on their customers, target audience, competitors, suppliers, and other market players, the role of data analysts becomes more important. To become a successful data analyst who can bring real value to the organization, you need to possess a specific set of skills.

How to Learn SQL for Marketing Analytics With LearnSQL.com

SQL is a valuable tool for any experts wanting to make data-driven decisions. Marketers are no exception. Let's explore how to design an effective learning path for SQL in marketing. SQL for marketing analytics is used to understand customers better and to increase the effectiveness of marketing campaigns. If you work in marketing and want to join other marketing experts who have already benefited from this tool, you need to learn SQL.

Use SQL for Data Analysis With the New Google Analytics 4

As Google is sunsetting its Universal Analytics in favor of Google Analytics 4, data analysts need to adapt and learn how to get the most from the new tool. In this article, I'll discuss how to enhance your data analysis by using SQL with Google Analytics 4. Universal Analytics by Google has been helping data analysts and marketers in all industries everywhere understand their audience better. However, Google recently announced they would stop their support of Universal Analytics on July 1, 2023.

These SQL Queries Will Help You With Data Analysis

Need to streamline your everyday data analysis tasks? This article explains how basic SQL queries can help. If you are planning a corporate career or any field that involves working with data, you must have come across SQL, or Structured Query Language. SQL was first developed in the 1970s and it continues to be the industry standard for database interactions. Many of you may already have decided to learn this language, given how powerful it is.

5 Tips for You From a Senior SQL Data Analyst

Are you looking for tips for becoming a better data analyst? Do you want to know about the mistakes and issues you may face? I have collected five tips for your everyday work based on my experience as a data analyst. You may have already read about what data analysts do, how much they earn, and how to become one. However, there is more to it than just becoming a data analyst.

Why Should Every Data Analyst Know SQL?

In the 1980s and 90s, it was the emergence of ERPs, processing a few thousand transactions a day. Now, sophisticated Cloud-based systems work with billions of transactions each day. How data is captured and handled has come a long way! Anybody who understands how to use this data has an edge. The good thing is that while the technology working in the background has become more complex, we don’t necessarily need to understand the underlying system’s details to use it.

Are You Ready to Become a Data Analyst?

Data analysts enjoy strong career prospects. Do you have the skills required for this role? Let’s find out! If you enjoy working with data, searching for interesting patterns and valuable insights, you may wonder “Should I become a data analyst?” In this article, I’ll explain what data analysts do and what skills a successful data analyst needs. What Does a Data Analyst Do? Data-driven organizations rely on specialists who know how to get value out of data.

Here’s How I Started Creating SQL Reports

Once upon a time, there was a girl who was just starting her adventure with learning SQL. As a marketer, one of her tasks was writing reports. Previously, she used Excel, a calculator, and written notes to prepare the reports her boss required. One day, it turned out that she could do her job much faster and easier. That was the day she read about SQL reports for the first time.

Here’s Why You Should Use SQL for Sales Analytics

Would you like to understand how your sales efforts play out so that you know where to put your focus? Do you want to empower your sales teams with sales analytics? This article shows you how you can use SQL to use your sales data to your advantage. If you work in sales, understanding the activities that produce results has financial consequences for you, your team, and your company. This is where sales analytics can really help you.

Still Using Excel for Data Analysis? See Why SQL Is Better!

Are you working with data and still using spreadsheets? Many people think that only programmers or professional data analysts can leverage SQL for data analysis. In this article, I’ll show how people with no IT background can use SQL for their daily work tasks. Not all people working with data have the corresponding job titles like data scientist, data analyst, or data engineer. Following the data democratization trend, almost all office workers do something with data as part of their daily duties – marketers analyze advertising campaigns, HR specialists analyze employee dynamics, auditors analyze credit portfolios, etc.

Top 10 Tools for Business Analytics

Business Analytics is one of today’s hottest career fields. However, success as a business analyst requires that you learn the right skills and software programs. Let’s see what tools you should know if you want to be a business analyst. With the world generating immense amounts of data – and having systems in place to capture and manipulate that data to fuel business growth – job opportunities for business analysts are only going to grow.

Why You Should Use SQL in Marketing Analytics

Have you been wondering how you could use SQL in your marketing data analysis work? Would you like to create SQL reports to guide your marketing decisions? In this article, you will learn how to use SQL for marketing through plenty of use cases. Are you a marketing professional wanting to better understand the results of your marketing efforts? Do you want better means to prove your point and demonstrate the value you create?

How Much Do Data Analysts Earn in 2021?

How Much Do Data Analysts Earn in 2021? How much does a data analyst earn? We did some data analysis ourselves. Nothing fancy, but it will give you some extra motivation for learning SQL for your data analyst gig. Data, data everywhere! We live in the world of (big) data. Having data is just the first step. Knowing what to do with it, how to interpret it, and what insights it holds, is true greatness.

Why You Should Work in a Data-Driven Company

Does accessing and using data collected by your company feel painful? Have you heard about data-driven companies? Working in a data-driven company may give you the ownership and the opportunities to use your company’s data. Read our article to learn more! If you work in a company, chances are that you want to do data analysis to solve problems. However, this is often not easy. You face many obstacles, impeding access to the data you need.

How SQL Can Help You Democratize Data in Your Company

Are you drowning in an ocean of data but lack the staff to find the treasures in it? Do bottlenecks clog your data and reporting processes? Have you heard about data democratization and wondered what all the fuss is about? In this article, we answer your questions! If you are a part of an organization that works with data, limited access is one of your biggest bottlenecks. It impedes data-related processes and prevents you from generating insights about your business.

Skills Every Data Analyst Should Have

If you’re a student looking for career advice or a specialist seeking new job opportunities, find out if a data analyst job is something worth considering. In today's article, I explain the essential skills required for data analysts and benefits that come from performing such a job. What Is a Data Analyst? Let’s start by defining exactly what a data analyst is. A data analyst is someone who uses their skills to collect, analyze, and report insights from company data.

Data Analyst vs. Data Engineer: A Full Comparison

Do you want to become a data analyst? Or maybe you dream about being a data engineer? Can't make up your mind? I'll help you. Read about the two roles’ history, their market situation, and the skills you need to become one. You already know that it's a good idea to enter the data world and work with databases. But how to do it? Behind which door is the better career waiting for you?

Why Does Your Company Need Data Analysis?

Data is the new gold. That is what the biggest in the business say, knowing the value of the data, the analyses, and the conclusions they bring. If you are wondering why your company needs data analysis and what value it could bring to your business, then this article is for you. Historically, many companies have gone into analytics mainly through financial and accounting data to improve revenue, reduce costs, and eventually increase profitability.

Analyze, Get Insights, and Make Money: SQL Data Analysis for Small Datasets

If you think SQL data analysis is useful only when a business is generating millions of rows of data – that SQL cannot help you if you are generating a limited dataset – think again and read on! There is so much talk about how SQL is useful in analyzing Big Data that sometimes the applications of SQL data analysis for small datasets can go unnoticed. Having worked with early-stage businesses – which have just started generating data through daily transactions – as well as big established clients generating terabytes of data, I can tell you for sure that SQL can be an extremely handy tool for just about any business.

6 Advanced SQL Queries for Analyzing Financial Data

Are you an advanced SQL user who’s new to finance? Do you want to learn how to use your knowledge to analyze financial data? The article will give you some guidance. You probably know that SQL is a potent tool for analyzing all sorts of data. The bigger and more complex data, the more beneficial SQL becomes. In certain situations, financial data can be very complicated; producing a sophisticated analysis requires sophisticated tools.

Why Use SQL Over Excel

SQL is replacing Excel in many fields, and data analysis is certainly one of them. If you are still using Excel as a data analyst, you are missing something very valuable. SQL can make your life easier, as it's more efficient and faster than Excel. So, how and from where can you learn SQL? How Can SQL Help Data Analyst? You can use SQL to help you with the following work:

SQL Indexing 101

Indexes are one of the most misused and misunderstood entities in physical database design. A good understanding of indexes and how they solve database performance problems is necessary for any database novice. In this article, we'll look at basic database indexes and their role in database development. To picture what an index is, consider a textbook. At the end of most textbooks is an index listing all the terms one can find in the text and the pages on which they appear.

How to Use a SQL Wildcard

SQL wildcard allows us to filter data matching certain patterns in SQL. We use SQL wildcards with the LIKE operator in the WHERE clause of a query to filter data. In this beginner’s article, we’ll look at everything you need to know about basic SQL wildcards. If you like playing cards, then you know that wildcards can substitute any other card in your deck. Similarly, SQL wildcards can substitute one or more characters.

Our Picks for 2020’s 7 Best Online SQL Schools

If you’re looking for the best online SQL courses but aren’t sure where to start, you’re in the right place. I evaluated the top 7 ranked SQL schools available online to help you find the right solution. While summer is a great time to relax and get away from work, it’s also an excellent opportunity to learn new skills – like SQL! Thanks to SQL schools putting their courses on the internet, learning new tech skills is super easy and you can choose from a variety of formats to suit your needs.

Why Learn SQL Over the Summer

Think summer is reserved for flying to warm places and hanging out at the beach? Sure! But it's also a great time to learn new skills that you haven't had time for. If you recently graduated from high school and want to get a head start on computer programming for college, learning SQL over the summer is a great opportunity. You have nothing to lose and everything to gain—SQL is actually really easy to learn, especially with so much free time over the summer.

Key Insights for Mastering SQL Queries Using Tinder Data Example

Going from zero to one can be daunting in any endeavor. The same is true for learning new programming languages, even simple ones like SQL. In this article, we’ll take a look at some key insights that will help you understand the nuances of mastering SQL queries. If you’ve never used SQL, you’re in the right place. When learning anything new, you’ll find that there are always some key insights or tips that can help you on your way.

Improving Slow Query Performance: When Runtime Matters

As SQL users, we usually focus on writing queries that return correct results. However, there are more things to consider when you're writing a query; one of them is query performance. In this article, we'll look at some examples where query response time is critical. Scene One: 911 Call Center Let's suppose we're at a 911 call center, when the phone rings. One of the operators answers the call; a witness reports that a man has been shot.

Converting Subqueries to Joins

Not all queries are alike, especially in terms of performance. In this article, we'll look at how you can convert SQL subqueries to joins for improved efficiency. When should I use SQL subqueries? Great question! Unfortunately, there's no concrete answer. SQL beginners tend to overuse subqueries. Typically, once they find that SQL construction works in one situation, they try to apply that same approach to other situations. It's only natural.

Learn to Write a SQL Correlated Subquery in 5 Minutes

If you’re familiar with the famous Russian nesting doll, then SQL correlated subqueries should be a peace of cake to understand—subqueries are just queries nested within queries. An SQL subquery is often called an “inner” query; the main query is usually called the “outer” query. This article covers everything you need to know about correlated subqueries. What Exactly is a SQL Correlated Subquery? A correlated SQL subquery is just a subquery that is executed many times—once for each record (row) returned by the outer (main) query.

How to Become a Database Analyst

Curious about becoming a database analyst? Maybe you've taken some database courses at university and they really struck a chord. Or maybe you learned online. Now you're thinking about making a career out of working with databases. Where would you start? What should you expect at each phase of your professional development? In this post, we'll explore the challenging and exciting world of databases analysis. We'll go from the very beginning of a career to the apex of professional success.

Extracting Data From a String: SPLIT_PART in PostgreSQL

Learn how to use split_part in PostgreSQL to extract data from strings. Quite often, we’d like to extract parts of a string when working with text values. A common example is when we have a full name and need to retrieve only the last name. In this article, we’ll examine how to do it using split_part in PostgreSQL, i.e. a string-related function that can be used to extract a substring.

High-Performance Statistical Queries: Dependencies Between Discrete Variables

In my previous article, we looked at how you can calculate linear dependencies between two continuous variables with covariance and correlation. Both methods use the means of the two variables in their calculations. However, mean values and other population moments make no sense for categorical (nominal) variables. For instance, if you denote "Clerical" as 1 and "Professional" as 2 for an occupation variable, what does the average of 1.5 signify?

Digging Into Data: Explore and Analyze Survey Results With SQL

Excel is a powerful beast that lets you analyze complex data. Yet, operating on big chunks of data can sometimes be a daunting task. Let's take a look at how SQL can help. Today, we'll tackle a common problem with importing data to an SQL database, using a real-life example. Suppose your company conducted a survey on the most popular programming trends and preferences, striving to meet the expectations of its users.

SQL Hacks To Control Family Budget On Black Friday Weekend

If you’re in the US, chances are you’ve been eagerly awaiting the approach of Black Friday just as much as Thanksgiving. Though the shopping frenzy takes hold of nearly everyone, some people have to stick to their budgets and shop prudently. In this article, we’ll take a look at how generating an SQL report can help you track how much your family spent shopping on Black Friday. Storing Black Friday Purchases in a Database Before we can create an SQL report, we first need some data we can use.

Introduction to Reporting with SQL — the Ultimate Tutorial for Business Professionals

Working with the financial aspects of large and small enterprises can be a daunting task for a business professional. In this article, we'll look at several ways of constructing the perfect SQL report. You've probably already heard about SQL from your colleagues or in other areas of your career. If you're here, you've likely concluded that learning SQL will make your professional life easier – and you're right!

SQL Statistical Analysis Part 1: Calculating Frequencies and Histograms

Database and Business Intelligence (BI) developers create huge numbers of reports on a daily basis, and data analyses are an integral part of them. If you wonder whether you can perform statistical analysis in SQL, the answer is ‘yes’. Read my article to learn how to do this! Statistics are very useful as an initial stage of a more in-depth analysis, i.e. for data overview and data quality assessment. However, SQL statistical analysis possibilities are somewhat limited as there are not many statistical functions in SQL Server.

Tag: Data analyst

Google Analytics and SQL

Google Analytics is a very popular tool among website and blog owners alike. With a simple and quick setup, it lets you gather data about your web page visitors easily. However, did you know that you can export data from Google Analytics to create your own SQL reports? Read this article to find out how. Google Analytics is an extremely popular and powerful solution that lets you collect and analyze various kinds of information about your website.

Should I Learn SQL as a Data Analyst?

So, you are a data analyst—someone who relies on data. You like to gather, clean, and transform data and come to conclusions based on data. You are a data detective. Which tool do you choose to do your job in an elegant, reproducible, and simple way? Excel? R? Python? Or should you learn SQL? Stay tuned! In this article, I will explain why SQL is a must-have skill for data analysts.

SQL Statistical Analysis Part 1: Calculating Frequencies and Histograms

Database and Business Intelligence (BI) developers create huge numbers of reports on a daily basis, and data analyses are an integral part of them. If you wonder whether you can perform statistical analysis in SQL, the answer is ‘yes’. Read my article to learn how to do this! Statistics are very useful as an initial stage of a more in-depth analysis, i.e. for data overview and data quality assessment. However, SQL statistical analysis possibilities are somewhat limited as there are not many statistical functions in SQL Server.

Tag: How SQL Can Help You Democratize Data in Your Company

How SQL Can Help You Democratize Data in Your Company

Are you drowning in an ocean of data but lack the staff to find the treasures in it? Do bottlenecks clog your data and reporting processes? Have you heard about data democratization and wondered what all the fuss is about? In this article, we answer your questions! If you are a part of an organization that works with data, limited access is one of your biggest bottlenecks. It impedes data-related processes and prevents you from generating insights about your business.

Tag: Data driven

Why You Should Work in a Data-Driven Company

Does accessing and using data collected by your company feel painful? Have you heard about data-driven companies? Working in a data-driven company may give you the ownership and the opportunities to use your company’s data. Read our article to learn more! If you work in a company, chances are that you want to do data analysis to solve problems. However, this is often not easy. You face many obstacles, impeding access to the data you need.

Tag: Data driven organization

How SQL supports data-driven organization

Typical business users make decisions based on gut feelings, but this can't get them so far. In this article, we'll look at how learning to write basic SQL queries helps your company become a data-driven organization. Businesses face many decisions. Do we increase our advertising budget in one region or the other? Are certain products selling quickly enough? What we should do if they aren't? Most of these decisions are driven by intuition, but organizations that make the most business impact use data-driven decision-making.

Tag: Data engineering

What Is the Future of the Data Engineer?

If you are wondering about the future of data engineering as a career and whether it is worth becoming a data engineer, then this article is for you. Here, I cover how lucrative the prospects are for data engineering and how you can get started and thrive in the domain. “Data” is probably one of the most used terms in our everyday business language today. A data engineer plays a pivotal role in developing the infrastructure required for data-related actions.

7 Things Every Data Engineer Should Know

People generate massive amounts of data every day. To get insights from data, organizations need to capture and process them efficiently. That is when data engineers are called up. In this article, I’ll discuss the data engineering role and the skill set necessary to succeed in the role. As the world generates more and more data every year, the IT industry creates new roles to deal with it. These roles include data analysts, data scientists, machine learning engineers, and data engineers.

An Overview of MS SQL Server Data Types

SQL Server data types define what can be stored in a column, local variable, expression, or parameter. It is essential to pick the right data type. Ultimately. your choice of data types affects the whole database. Read on to learn about all of the data types available in MS SQL Server. In this article, we’ll cover numerical, text, and date and time data type categories in detail. We’ll go through their syntax, storage size, and typical use cases.

New to Data Engineering? Don't Make These Mistakes

It's best to learn from the mistakes of others. This advice also works for data engineering. In this article, you'll find tips to help you advance your career and avoid common data engineering mistakes. The data revolution has produced tremendous opportunities and created various high-paying jobs related to the collection, maintenance, and manipulation of data. Data engineering is one of the most lucrative and interesting jobs of this family.

What Is the Difference Between a Primary Key and a Unique Key?

When designing a database, we often need to decide between defining a primary key vs. a unique key. Both of them are crucial during the design and further phases of a database. They allow us to uniquely identify each row, ensure the uniqueness of values in the column(s), and more. Let’s take a deep dive to learn more. This article will go through the primary and unique keys, their functions, and features.

Data Analyst vs. Data Engineer: A Full Comparison

Do you want to become a data analyst? Or maybe you dream about being a data engineer? Can't make up your mind? I'll help you. Read about the two roles’ history, their market situation, and the skills you need to become one. You already know that it's a good idea to enter the data world and work with databases. But how to do it? Behind which door is the better career waiting for you?

What Is a NOT NULL Constraint in SQL?

SQL has several ways of dealing with NULLs. In this article, we’ll focus on the NOT NULL constraint and other NULL-related clauses. Understand this and you’ll take an important step in your SQL growth! Before we get straight into the NOT NULL constraint, let’s quickly define what NULLs and constraints are. NULL values are a central concept in SQL databases. The idea behind a NULL value is simple: a NULL value means that we do not have a known value for that field.

What Is a Unique Constraint in SQL?

To ensure the uniqueness of data in a database, we use the SQL UNIQUE constraint. In this article, we’ll discuss how, when, and why to implement it. The idea of a unique constraint is not unique to SQL; it’s a familiar concept in real life, although we probably call it something else! For example, think of ID numbers. There can be only one social security number (SSN) per person and each one must be unique.

Data Types in SQL

Read this article and learn the ABC of SQL data types. Data types are used to define the type of data stored in a database. However, there are related concepts that a good SQL developer should know: data type conversion, what operations are possible between different data types, date arithmetic, etc. SQL also provides functions that manipulate values of different data types (i.e. functions for string data, date and time data, etc.

What Is Auto-Increment in SQL?

In this article, we’ll learn the basics of the auto-increment feature of SQL: what it is and how to use it efficiently. One of the many features offered by SQL is auto-increment. It allows us to automatically generate values in a numeric column upon row insertion. You could think of it as an automatically supplied default value – the next number in a number sequence – that’s generated when the row is inserted.

LearnSQL Track of the Season: Creating Database Structure

New year, new challenges, and ... a new SQL Track of the Season! Start 2021 by learning SQL and data engineering. In this article, we answer frequently asked questions about our Creating Database Structure track. Maybe you haven't noticed yet that there’s an order to many LearnSQL.com courses; you can learn SQL by doing them in the right order. We call this option our ‘SQL tracks’. These are logically structured and well-thought-out learning paths that will help you take the next steps towards becoming an SQL expert.

What is an SQL View?

A view is a well-known feature in SQL. It allows you to create a virtual table based on an SQL query referring to other tables in the database. A view stores an SQL query that is executed whenever you refer to the view. This is a convenient way to get the desired data because it is easier to run a query stored in a view than to type a query from scratch.

What Is a Foreign Key in SQL?

What does a foreign key do in SQL? Why would you need one? Learn the ABCs of foreign keys in five minutes. Foreign keys are a central concept in SQL databases; they allow us to enforce data consistency. Usually they work with primary keys to connect two database tables, like a virtual bridge. All SQL developers need to know what SQL foreign keys are, how they work, what data values are allowed in them, and how they’re created.

What Is a SQL Constraint?

What are SQL constraints? When and why should you use them? We give examples of common constraints and demonstrate how to apply them. When you’re creating a relational database, you often want to impose certain restrictions on some columns. For example, a column containing a social security number should store only unique values; a column containing a date of birth should not be null, or left empty. These conditions can be ensured by using SQL constraints.

Top 7 Online Courses for Data Engineers

This article summarizes the top online courses available for data engineers. We have picks suitable for beginners as well as intermediate learners. If you’re interested in database design and management, check these courses out! Most individuals who aspire to enter the realm of data aim for data scientist or data analyst roles. While these roles are indeed very rewarding because of their tangible links to customers and business direction, the role of data engineers is equally vital for businesses that operate in a data-rich environment.

What is a Primary Key in SQL?

Primary keys are an important concept in SQL databases. They provide a unique ID for every row in a database table. As an SQL developer, you should know what primary keys are, what data values are allowed in them, and how to create them. Read this article to learn the ABCs of primary keys in 10 minutes. How to Identify Rows in a Table Tables are the main objects in an SQL database, and as you probably know, tables store records or rows.

What Is a DBMS?

We generate vast quantities every day, and that data needs to be stored somehow. That’s where DBMSs come in handy. Find out what they are and how they relate to databases. If you go on a diet and simply want to keep track of your weight, you can probably use a piece of paper and a pencil. If you then want to chart your daily caloric intake, you’ll probably switch to something like a computer spreadsheet.

How to Create Your First Table in SQL

Creating a database table with SQL is one of the core skills you’ll need to work with data. And it’s easy to learn, so let’s get started! Imagine you’re analyzing data and want to store your results in a database table. Sure, you've done this a million times in Excel. But you’re not sure how to create a table with SQL. Or maybe you’ve noticed that data engineering is in high demand and you want to start learning its core concepts.

How Much Do Data Engineers Earn in 2020?

Data engineering is a hot job right now. What does a data engineer do? And just how much do they earn? We’ve done the research for you. If you are reading this, you’re either starting to learn SQL or you already know some and feel it’s time to look around for a SQL job. Maybe you’re in the midst of tackling our Creating Database Structure track. And, let’s be honest, maybe you need some extra motivation to keep on you track.

How to Create a Table in SQL

Creating tables in databases is a very helpful skill, and not just for software engineers or database administrators. It allows you to design or change the structure of a database and store data that’s related to each other. In this article, you’ll learn what a database table is, who creates them, and how to use the syntax of the CREATE TABLE command. What Is a Database Table? A relational database is built of various structures like tables, views, procedures, and triggers.

Who Is a Data Engineer?

A new kind of job has recently emerged in the IT world: Data Engineer. At first sight, it may seem very similar to Data Analyst or Data Scientist positions. However, our article explains all the important differences. We present the skills, tools, and everyday tasks of Data Engineers. We also explain how you can get started with this career path.   Thirty years ago, we typically used terms such as “Computer Scientist” when referring to anyone working with computers.

LearnSQL.com’s New Learning Path: Data Engineering

Calling all future data engineers! Would you like to learn to use SQL? Then our new Data Engineering Learning Path is just for you! We’re very excited to announce the release of a new learning path at LearnSQL.com: Data Engineering, published in July 2020. This is the second learning path offered in our platform. So far, we offered an analytical path, SQL Querying & Reporting, that focuses on writing queries and business reports in SQL.

What Is Data Engineering?

Data Engineering is a fairly new term in IT. And it’s getting more and more attention. You may have heard about a few similar fields like data science, Big Data, and machine learning. This article explains the difference between these concepts and shows how they can be combined to analyze vast amounts of data. When computers first appeared, their storage capacity was very limited. Do you remember floppy disks? They were popular in the late 20th century and typically offered around 1.

TRUNCATE TABLE vs. DELETE vs. DROP TABLE: Removing Tables and Data in SQL

What’s the difference between truncating, deleting, and dropping a table in SQL? Find out in this article. There are a lot of ways to delete data in SQL, including the DELETE, TRUNCATE TABLE and DROP TABLE commands. Which one should you use in a given situation? In this article, you’ll learn the syntax of each command in different database engines like MySQL, PostgreSQL, SQL Server, and Oracle. And you’ll understand the DROP TABLE vs.

Tag: Data modifying

Simplify SQL Code: Recursive Queries in DBMS

Hey SQL users! Are you repeating the same query in every report? Are your queries getting too complicated? Use recursive queries to simplify SQL code! Too many SQL reports can lead to clutter on your desktop and in your head. And is it really necessary to code each of them separately? Ad-hoc queries can share much of the same SQL code with managerial reports and even regulatory reports. Suppose you’ve been writing basic SQL code for a while.

Using CASE with Data Modifying Statements

What happens when you combine CASE with SQL's data modifying statements? Find out in this article. The CASE expression is a very useful part of SQL and one that you'll employ frequently. We've already covered what the CASE expression does, how to format it, and how to use it in a SELECT statement in "Using CASE to Add Logic to a SELECT". Another article, "How to Sort Records with the ORDER BY Clause"

Tag: Data quality

Extracting Data From a String: SPLIT_PART in PostgreSQL

Learn how to use split_part in PostgreSQL to extract data from strings. Quite often, we’d like to extract parts of a string when working with text values. A common example is when we have a full name and need to retrieve only the last name. In this article, we’ll examine how to do it using split_part in PostgreSQL, i.e. a string-related function that can be used to extract a substring.

How to Remove Junk Characters in SQL

Unwanted characters in text data can be a bit of a pain, but there’s an easy way to fix them. Scroll down to learn how to remove junk characters in SQL in the easiest way! Sometimes, we’ll find unwanted characters inside our string data because our SQL queries didn’t work as expected. Moreover, these extra characters may sometimes be invisible, which really complicates things. In this article, we’ll examine some string-related SQL functions that can handle unwanted characters—visible or not!

How to Solve Capitalization Data Quality Issues

Misspelled names, typos, and text data quality issues in your database? Power up your queries! Use SQL string functions to address data quality issues related to capitalization. Sometimes, our SQL queries don't work as expected because of data quality issues. In this article, we will examine some string-related SQL functions that can correct data quality issues related to capitalization. We'll be using PostgreSQL in our examples, but similar functions are available in most database engines.

Tag: Data science

Learn SQL for Data Science With LearnSQL.com

If you are interested in a data science career and have looked at a few relevant job descriptions, you've probably noticed many leading tech companies expect their data scientists to know SQL. Let's see how you can learn SQL for data science and become more valuable to any data-driven organization. A data scientist is a complex technical role that expects a combination of the skills of a statistician, a business analyst, and an IT expert.

Tag: Data types

Understanding Numerical Data Types in SQL

Working with databases of any kind means working with data. This data can take a couple of predefined formats. As you start on your learning path with LearnSQL.com, you will start to understand SQL's different data types. In this article, we will cover different variations of the SQL numeric data type. We'll also examine some functions that convert data from one type to another. Creating tables is the first step in any SQL coding project.

How to Recognize SQL Text Data Type

How can you store textual information in database tables? Thanks to this post, you’ll learn the characteristics of every text data type in SQL Note: This post is intended for readers familiar with SQL data definition language (DDL) and the DDL CREATE statement. To learn more about DDL, check out LearnSQL.com. Most data types are classified as NUMERIC, CHARACTER, or DATE. In this post, we’re going to focus on each CHARACTER or text data type in SQL.

Tag: Data warehouse

How to Join Tables in SQL Without Using JOINs

Here’s how you can combine tables without the JOIN keyword. It seems like it shouldn’t be possible: join tables in SQL without using the JOIN keyword. But using the JOIN keyword is not the only way to join tables in SQL. This article will show you two additional methods for joining tables. Neither of them requires the JOIN keyword to work. They are: Using a comma between the table names in the FROM clause and specifying the joining condition in a WHERE Using UNION/UNION ALL.

Tag: Database

The Most Popular Databases for 2022

With the number of database products increasing with each passing year, it is important to understand which database best fits your use case. This article lists the top-ranking databases available in the market today. When something that first became popular in the early 1980s is not slowly fading away but is still evolving and becoming more relevant, you know it had to be an important invention. The database is no exception.

Tag: Date and time

Useful SQL Patterns: Date Generator

As you start coding in SQL, you will use some statements and techniques over and over again. We call these “SQL patterns”. This series will look at the most common SQL patterns and consider how to use them. SQL patterns, such as the pivot pattern we discussed last week, can save you a lot of time and effort. Suppose you are asked to get a range of days in a financial quarter, but the only records you have are for the start and end dates of each quarter.

Performing Calculations on Date- and Time-Related Values

Relational databases support several date and time data types. In this article, we'll look at several arithmetic operations we can do on these types. These operations are logical and understandable, even for the beginning SQL coder. Let's first briefly explain the main data types used for dates and times. Keep in mind that data types may differ by database engine, so check your database documentation for specifics before you start working with them.

The Most Useful Date and Time Functions

Date and time functions and formats are quite different in various databases. In this article, let's review the most common functions that manipulates dates in an Oracle database. The function SYSDATE() returns a 7 byte binary data element whose bytes represents: century, year, month, day, hour, minute, second It's important to know that select sysdate from dual in SQL*Plus gives the same result as select to_char(sysdate) from dual because SQL*Plus binds everything into character strings so it can print it.

Tag: Date arithmetic

The SQL Coalesce Function: Handling Null Values

You may already know how to return null values in SQL. Now, we’re going to learn how to do the opposite. Though the SQL COALESCE function may seem complex, it’s actually very straightforward and useful. Let’s look at several examples of how the SQL COALESCE function can be used to work with NULL values in SQL. The Need for Coalesce in SQL Before we dive into the SQL COALESCE function in detail, you should understand how NULL values behave in expressions.

How Often Employees Are Running Late for Work: SQL Datetime and Interval SQL Arithmetic

Computing Tardiness: Date, Time, and Interval SQL Arithmetic In this article, we’re going to discuss some interesting operations we can perform with date-related data types in SQL. The SQL standard, which most relational databases comply with these days, specifies the date-related data types that must be present in relational databases. The most important of such data types are date, time, timestamp, and interval. Here’s a brief rundown of the differences between these data types:

Tag: Date functions

18 Useful Important SQL Functions to Learn ASAP

Beginning with SQL: Useful Functions to Master Learning a new programming language can seem intimidating. Like any other language, a programming language has a large vocabulary that you need to master. In this article, we'll look at some of the most useful SQL functions that you need to know. There are many useful SQL functions for working with different data types. Once you practice with some of the most common ones, you'll gain enough confidence to move on to more advanced material.

Tag: Delete

What Is the DELETE Statement in SQL?

This article will explain the use of the DELETE statement, one of the primary methods of removing existing records from your database. First we will run through the syntax, followed by some easy-to-understand examples. The DELETE statement in SQL is extremely useful. It allows you to remove any obsolete or “bad” data from your database tables. You should exercise caution when using the DELETE statement, as the operation is not reversible.

Learn SQL Views in 30 Minutes

Views aren't complicated – if you've got half an hour, we'll get you started writing SQL queries using views! Let's start by answering the question "What is a view in SQL?'. A view is a database object (as is a table, an index, or a stored procedure). Like a table, you can query a view and extract the information in it. It can be used in the FROM clause of a SELECT, and you can reference view columns in clauses like SELECT, WHERE and GROUP BY among other clauses as well.

Using CASE with Data Modifying Statements

What happens when you combine CASE with SQL's data modifying statements? Find out in this article. The CASE expression is a very useful part of SQL and one that you'll employ frequently. We've already covered what the CASE expression does, how to format it, and how to use it in a SELECT statement in "Using CASE to Add Logic to a SELECT". Another article, "How to Sort Records with the ORDER BY Clause"

Tag: Distinct

What’s the Difference Between UNIQUE and DISTINCT in SQL?

We use the words unique and distinct interchangeably in our day-to-day life. However, these words play very different roles in SQL. Let’s find out what is so different about them and how we can use them in SQL. Despite the words unique and distinct being synonyms, they cover very different things in SQL. The UNIQUE keyword in SQL plays the role of a database constraint; it ensures there are no duplicate values stored in a particular column or a set of columns.

What Is the Role of DISTINCT in SQL?

The DISTINCT keyword in SQL plays an important role in removing duplicate values from your results. This article provides examples showing exactly how DISTINCT works. By default, SQL queries show all the returned rows, including duplicate rows, in the result set. The DISTINCT keyword in the SELECT clause is used to eliminate duplicate rows and display a unique list of values. In other words, the DISTINCT keyword retrieves unique values from a table.

Tag: Division

How the Division Operator Works in SQL

The division operator in SQL is used to divide one expression or number by another. This article will show you exactly how to use it and common mistakes to avoid along the way. The division operator in SQL is considered an arithmetic operator. The arithmetic operators are addition (+), subtraction (-), multiplication (*), division (/), and modulus (%). This article will focus on the division operator, discussing the rules that must be followed along with some common mistakes to look out for when trying to divide in SQL.

Tag: Duplication

How to Track Down Duplicate Values in a Table

When it comes to information management, duplicates present one of the most common challenges to data quality. In this article, I'll explain how it is possible to find and distinguish duplicate names with the help of the SQL data programming language. I really like my maiden name. The reason I like it so much is because it's rare. My maiden name (first with last) provided a unique identifier on platforms such as LinkedIn, Facebook, Twitter and similar.

Tag: E learning

How to Practice SQL with LearnSQL.com

Practicing new skills online needs motivation and self-discipline, but it’s worth it. We’re facing a difficult, uncertain time. On one hand, the COVID pandemic caused a lot of fear. What will happen in the future? Will I keep my job? Will we stay safe and healthy? On the other hand, COVID is giving us a lot of time. Working remotely, not having anything to do but stay home and… And what?

Top 5 Beginner Online SQL Courses in 2020

Looking for an exciting new career? Data analysis won’t disappoint you! The simplest way to make this possible is by learning SQL, and online SQL courses are the most effective learning method. Don’t know where to start? Here’s an overview of the best online SQL courses for complete beginners. There are infinite reasons for changing your industry. You may want to land a new job because you’re burnt out. You may be bored and want something more challenging.

Choose the Best Way to Learn SQL

SQL has become a hot topic in the professional world, and many resources have appeared both online and offline for learning SQL. It’s easy to get lost in the jungle of books, tutorials, and courses. Which resources do you choose? If you want to know how to learn SQL quickly and effectively, take a look at my list. There are many reasons for learning SQL. We asked our users about them and learned that there was no universal motive.

Online Education in the Times of COVID-19

LearnSQL.com grants free access to their Interactive courses till 04/20/2020. People around the world are faced with a new challenge. A challenge which requires swift action and adaptability. Students and teachers, employers and employees, families and friends. Many have shown vigilance and decisiveness, while at the same time trying their best to maintain their everyday-life continuity. However, there are those who, due to the current circumstances, need to postpone plans and invest their resources in different areas.

Stay at Home and Learn SQL for Free with LearnSQL.com

Working remotely is a dream come true for some. You ditch commuting and have more time for the people you love and the things you enjoy. For others, it's a challenge to maintain their focus when there are new distractions. It's also an opportunity to invest the few gained hours in learning something new. Staying at home can be a time when you might find yourself busier than you've ever been, but not getting many things done, and worse, not learning what you planned to.

What Programming Language Should You Learn?

If you've ever been wondering which programming language you should learn first, you know that's a tough nut to crack. It’s especially difficult if you are new to IT and programming. In this article, I give suggestions for what to learn first and what perspectives each language can give you in IT. There are hundreds of programming languages, and new ones are showing up all the time. Getting to know all of them is simply impractical and impossible.

How to Study Online: 5 Steps to Becoming an Effective Learner

If you suffer from procrastination or lack of motivation, you’re not alone. We have some online learning tips to make your learning journey smoother and more enjoyable. One of the best things about being an adult is that we can do what we want: go to sleep late at night, party until morning, eat junk food. Besides all those small pleasures, as adults we are responsible for ourselves, our choices, and our mistakes.

Tag: Edgar codd

51 Years of Relational Databases

If it weren't for him, there would be no modern databases. It is the 51st anniversary of the publication of his article that changed the rules of the game. Edgar Frank Codd is one of the fathers of SQL, and his name is one of the first to be mentioned in the history of databases. Or maybe even the history of computer development in general? See what we owe to Dr.

Tag: Elearning

A Non-Technical Introduction to Learning SQL on Your Lunch Break

Do you think learning SQL will help you in your career? You are right. SQL is one of the easiest computer languages to learn. These days many non-IT employees have SQL skills and use them to extend their professional capacity. Moreover, more and more companies are encouraging their employees in non-IT areas (like sales, advertising, and finances) to learn and use SQL. One of the benefits of empowering employees with SQL skills is that once you answer one data question, the results will generate a new data question, and then perhaps a cascade of further data questions.

SQL Mythbuster – 5 Reasons Why No One Should Be Afraid of SQL

Anyone can learn SQL. It’s not as hard as you think! In today’s world, even those in non-technical jobs need some technical skills. And you don’t have to be a hard-core nerd to get these skills. Let me tell you my own story. A few years ago, I wasn’t considering learning SQL or anything else that I labelled “technical”. My background is in sociology, journalism, and scriptwriting, and I thought computer languages were pretty sci-fi.

How to Learn SQL: 6 Ideas for Newbies

Learning a new skill can be a daunting task, especially in programming. SQL is not immune to this. Luckily, with the Internet and the explosion of programming-related information out there, there are a lot of options you can use to undergo your SQL training! But we then come to a new roadblock. Where to begin? How will we know which option is best for our budget, skill level, and schedule?

Tag: Extras

SQL INSERT, SQL UPDATE, SQL DELETE – Oh My!

Need to understand SQL INSERT, UPDATE, or DELETE? We'll get you up to speed with a comprehensive How-To and useful examples! SQL INSERT, UPDATE, and DELETE statements—what are they all about? If you're a data engineer, a database administrator, or even just your average data fanboy or girl, one day you're going to find yourself with a database that becomes your "baby." Charged with this special bundle of joy, you're going to need to feed and change the little fella.

SQL, Databases, and Hollywood Movies

Policemen, doctors, lawyers, scientists, teachers: These are the professions that we often see in Hollywood movies. But are movies also trying to show what the work of data analysts looks like? Here is a list of six movies in which screenwriters, directors, and producers decided to cast SQL and databases in the main roles. Data analysis is most often associated with business, reporting, and making key decisions for the company.

Career Change: From Accountant to Database Designer

How do career changes and life choices impact our future? Can we change the path that's been set for us? And if so, where do we begin? I wouldn't blame you if you thought this article is about change. In a sense, it is—it's in the title, after all. But for me, this article is more about what remains constant. If somebody were to ask me what hasn't changed for me since my childhood, I would know the answer immediately: curiosity.

Forget About Excel, High Five With SQL

Find out why you should forget about Excel and start using SQL even if you're not an IT expert. We'll show you how easy it is to learn SQL, how it can make you work better, and how LearnSQL.com makes the learning process fun. "I Don't Deal With Data" We frequently hear the sentence above from people outside the IT industry. Well, it's not entirely true. Data is now almost everywhere.

How to Install PostgreSQL on Windows 10 in 5 Minutes

It may look like a complicated task to install PostgreSQL, Oracle, or SQL Server or any other database software, but it really isn’t! These days, most relational database management systems come with installation wizards that make the process much simpler. In this article, we’ll look at how to install PostgreSQL and test that the installation is working. Install PostgreSQL: Steps Involved To install PostgreSQL, we’ll complete the following tasks:

Our Picks for 2020’s 7 Best Online SQL Schools

If you’re looking for the best online SQL courses but aren’t sure where to start, you’re in the right place. I evaluated the top 7 ranked SQL schools available online to help you find the right solution. While summer is a great time to relax and get away from work, it’s also an excellent opportunity to learn new skills – like SQL! Thanks to SQL schools putting their courses on the internet, learning new tech skills is super easy and you can choose from a variety of formats to suit your needs.

Why Learn SQL Over the Summer

Think summer is reserved for flying to warm places and hanging out at the beach? Sure! But it's also a great time to learn new skills that you haven't had time for. If you recently graduated from high school and want to get a head start on computer programming for college, learning SQL over the summer is a great opportunity. You have nothing to lose and everything to gain—SQL is actually really easy to learn, especially with so much free time over the summer.

Essential SQL Terms to Know for Beginners and Pros

Working with databases can seem daunting to a non-technical person. Right away, you’re bombarded with new terms that make your head spin. Database, database instance, table, SQL and others are some of the basic terms that you need to understand just to have a normal conversation with your technical colleagues. In this article, we’ll explore some basic SQL database terminology you need to know to succeed. Imagine you’re attending a meeting with the development staff and suddenly feel as if you’re listening to white noise.

15 Best SQL Articles for Beginners Published in 2017

For this post, I've gathered 15 of the most interesting SQL articles published in 2017. If you're looking for articles on SQL for beginners, want to learn more about databases and SQL queries, or just expand your knowledge of SQL, this article is perfect for you. Let's dive right in! Top 3 Vertabelo Academy Articles I'll start off the list with three of the most popular Vertabelo Academy SQL articles.

How to Draw a Christmas Tree in SQL

You can use SQL to manipulate all kinds of data, from huge analytical queries to brief single-purpose statements. But you can also use SQL just for fun, without any business requirements stifling your creativity. So, get out your jolly hat and prepare to sing O Christmas Tree as we create some quirky art with plain old SQL. Today, we’re going to generate some holiday-themed ASCII art, just for fun. That’s right.

SQL Hacks To Control Family Budget On Black Friday Weekend

If you’re in the US, chances are you’ve been eagerly awaiting the approach of Black Friday just as much as Thanksgiving. Though the shopping frenzy takes hold of nearly everyone, some people have to stick to their budgets and shop prudently. In this article, we’ll take a look at how generating an SQL report can help you track how much your family spent shopping on Black Friday. Storing Black Friday Purchases in a Database Before we can create an SQL report, we first need some data we can use.

What Is Vertabelo’s SQL Cheat Sheet?

Everyone, from rookie programmers to SQL ninjas, needs a bit of help now and again. Enter Vertabelo's SQL Cheat Sheet! Working with databases is hard. There's a lot of data to manage, which can be daunting. But the main challenge many database users face is the SQL commands themselves. It's all right when you're using the same familiar ones day after day, but what about the commands you dust off once or twice a year?

The 5 Highest Paying Jobs That Use SQL

IT provides a wide and growing job market, offering many excellent opportunities in both career development and earning potential. Today we’ll take a look at several very interesting types of database jobs that use SQL. Every year, many in the work force set their sights and aim for new and better jobs. When it comes to jobs, “better” means different things to different people, but earning potential is almost always a top priority.

SQL Mythbuster – 5 Reasons Why No One Should Be Afraid of SQL

Anyone can learn SQL. It’s not as hard as you think! In today’s world, even those in non-technical jobs need some technical skills. And you don’t have to be a hard-core nerd to get these skills. Let me tell you my own story. A few years ago, I wasn’t considering learning SQL or anything else that I labelled “technical”. My background is in sociology, journalism, and scriptwriting, and I thought computer languages were pretty sci-fi.

5 Books That Will Grow Your SQL Skills

Which books will help you build your database skills? We look at five awesome SQL books. There’s a common saying that “all wise men read books”. I would say that all professionals read books – particularly those related to their field. There are many books about databases and SQL; most are tied to specific vendors (DB2, Oracle, MS SQL) but there are also plenty that are vendor-neutral. In this article, I’m going to review a few books that I would recommend to SQL learners at various levels of proficiency.

Should I Learn SQL? 4 Convincing Reasons

There are 250+ computer programming languages in popular use. Why should you learn SQL, or Structured Query Language? Why Should You Learn SQL? Why learn SQL? To answer this question, you should start with reflecting on your professional life. Are you interested in boosting your career? Wondering what skills are worth investing in? If you’re currently in your dream job, still searching for it, or even thinking about starting your own business, it pays to develop your technical skills.

Tag: Fact table

How to Join Tables in SQL Without Using JOINs

Here’s how you can combine tables without the JOIN keyword. It seems like it shouldn’t be possible: join tables in SQL without using the JOIN keyword. But using the JOIN keyword is not the only way to join tables in SQL. This article will show you two additional methods for joining tables. Neither of them requires the JOIN keyword to work. They are: Using a comma between the table names in the FROM clause and specifying the joining condition in a WHERE Using UNION/UNION ALL.

Tag: Fetch

Oracle Top-N Queries for Absolute Beginners

It's common to run a query using only part of a dataset – for example, the top 100 salespeople in a company. In this article, we'll see how to use Oracle's Top-N query method to query just these rows. Top-N queries retrieve a defined number of rows (top or bottom) from a result set. In other words, they find the best or worst of something – the ten best selling cars in a certain region, the five most popular routers, the 20 worst-performing stores, etc.

Tag: Foreign key

What Is the Benefit of Foreign Keys in SQL?

What is a foreign key and why is it so important in relational databases? Learn all the details about foreign keys in this article. One of relational databases’ key features is the ability to link data stored in different tables. These links, called references, essentially act as connections between tables. They are created using the FOREIGN KEY constraint on table columns. In this article, we’ll learn what the FOREIGN KEY constraint does in SQL.

Referential Constraints and Foreign Keys in MySQL

Foreign keys and referential constraints allow you to set relationships between tables and modify some of the database engine’s actions. This beginner’s guide explains referential integrity and foreign key use in MySQL. One of the most important aspects of database usage is being able to trust the information you store. Database engines provide several features that help you maintain the quality of your data, like defining required columns as NOT NULL and setting an exact data type for each column.

Tag: Free sql course

Stay at Home and Learn SQL for Free with LearnSQL.com

Working remotely is a dream come true for some. You ditch commuting and have more time for the people you love and the things you enjoy. For others, it's a challenge to maintain their focus when there are new distractions. It's also an opportunity to invest the few gained hours in learning something new. Staying at home can be a time when you might find yourself busier than you've ever been, but not getting many things done, and worse, not learning what you planned to.

Tag: Functions for manipulating sql strings

5 SQL Functions for Manipulating Strings

SQL functions used for manipulating strings, commonly called string functions, are among most important SQL’s tools. In this post, we’ll look at five ways you can perform various operations on strings. There are many SQL functions that let you “edit” string data. As you learn SQL, you’ll see how useful they prove. Some sql trim off unneeded spaces or characters; others tell you how long a string is. These functions give you a lot of opportunities to transform and work with strings, which makes your code more effective.

Tag: Game

Can SQL Help Solve Crossword Puzzles?

Everyone has solved crossword puzzles and has certainly had some problems finding an appropriate word. Thanks to SQL, it is ridiculously simple to quickly dispel your crossword doubts and give you the correct answers. Of course, Google is commonly known as a universal cure for many doubts, but handling the problem yourself is much more rewarding. Recently I came across some simple and interesting examples from Andrew Cumming's book "

Tag: Generators

Useful SQL Patterns: Date Generator

As you start coding in SQL, you will use some statements and techniques over and over again. We call these “SQL patterns”. This series will look at the most common SQL patterns and consider how to use them. SQL patterns, such as the pivot pattern we discussed last week, can save you a lot of time and effort. Suppose you are asked to get a range of days in a financial quarter, but the only records you have are for the start and end dates of each quarter.

Tag: Get started

How to Install Microsoft SQL Server 2019 and SQL Server Management Studio

Do you want to install SQL Server 2019 on your Windows PC? How about the latest version of SQL Server Management Studio? I’ll walk you through the process. Soon you’ll be writing T-SQL queries and operating on SQL Server databases! As I write this article, Microsoft SQL Server 2019 is the latest version of SQL Server. It’s the 15th version of one of the most popular database servers in the world.

Join us on Facebook–We Can Learn More Together

We are so happy that you have joined us to learn and develop your SQL skills! We want to invite you to a new Facebook group, We Learn SQL. It is a great place for anyone interested in meeting like-minded people who also want to learn about database-related concepts. Learning together is easier, don't you think? Joining this group is a great opportunity to begin sharing your learning experiences with others.

YouTube Tutorials That Actually Teach You Some SQL

YouTube is not just funny cats, music clips, and viral videos. It can also be a mine of knowledge – if you know where to look. Can YouTube tutorials really help you learn SQL? Let's say you're a marketer or an accountant. You work with databases every day. But when it’s time to write a query and get specific data, you need to call someone from IT. Why not learn to do it yourself?

Career Change: From Accountant to Database Designer

How do career changes and life choices impact our future? Can we change the path that's been set for us? And if so, where do we begin? I wouldn't blame you if you thought this article is about change. In a sense, it is—it's in the title, after all. But for me, this article is more about what remains constant. If somebody were to ask me what hasn't changed for me since my childhood, I would know the answer immediately: curiosity.

Forget About Excel, High Five With SQL

Find out why you should forget about Excel and start using SQL even if you're not an IT expert. We'll show you how easy it is to learn SQL, how it can make you work better, and how LearnSQL.com makes the learning process fun. "I Don't Deal With Data" We frequently hear the sentence above from people outside the IT industry. Well, it's not entirely true. Data is now almost everywhere.

A Non-Technical Introduction to Learning SQL on Your Lunch Break

Do you think learning SQL will help you in your career? You are right. SQL is one of the easiest computer languages to learn. These days many non-IT employees have SQL skills and use them to extend their professional capacity. Moreover, more and more companies are encouraging their employees in non-IT areas (like sales, advertising, and finances) to learn and use SQL. One of the benefits of empowering employees with SQL skills is that once you answer one data question, the results will generate a new data question, and then perhaps a cascade of further data questions.

How to Install PostgreSQL on Windows 10 in 5 Minutes

It may look like a complicated task to install PostgreSQL, Oracle, or SQL Server or any other database software, but it really isn’t! These days, most relational database management systems come with installation wizards that make the process much simpler. In this article, we’ll look at how to install PostgreSQL and test that the installation is working. Install PostgreSQL: Steps Involved To install PostgreSQL, we’ll complete the following tasks:

How SQL supports data-driven organization

Typical business users make decisions based on gut feelings, but this can't get them so far. In this article, we'll look at how learning to write basic SQL queries helps your company become a data-driven organization. Businesses face many decisions. Do we increase our advertising budget in one region or the other? Are certain products selling quickly enough? What we should do if they aren't? Most of these decisions are driven by intuition, but organizations that make the most business impact use data-driven decision-making.

Microsoft SQL Server 2017 Installation Step by Step

Microsoft SQL Server is one of the most popular professional database servers on the market. In this guide, I’ll show you all SQL Server 2017 installation steps to help you install it on the Windows operating system together with SQL Management Studio. If you want to learn T-SQL, the dialect of SQL used in SQL Server, check out our SQL from A to Z in MS SQL Server track.

How to Begin Running SQL Queries

In this article, I’ll explain how to run a SQL query to help you execute your first one. Let’s jump right in! Running SQL queries for the first time is not a complex task, but it can seem intimidating at first if you’re a complete beginner. But once you get past that initial roadblock, you’ll be able to focus on learning SQL and writing more interesting queries to meet your business needs.

How to Use a SQL Wildcard

SQL wildcard allows us to filter data matching certain patterns in SQL. We use SQL wildcards with the LIKE operator in the WHERE clause of a query to filter data. In this beginner’s article, we’ll look at everything you need to know about basic SQL wildcards. If you like playing cards, then you know that wildcards can substitute any other card in your deck. Similarly, SQL wildcards can substitute one or more characters.

Our Picks for 2020’s 7 Best Online SQL Schools

If you’re looking for the best online SQL courses but aren’t sure where to start, you’re in the right place. I evaluated the top 7 ranked SQL schools available online to help you find the right solution. While summer is a great time to relax and get away from work, it’s also an excellent opportunity to learn new skills – like SQL! Thanks to SQL schools putting their courses on the internet, learning new tech skills is super easy and you can choose from a variety of formats to suit your needs.

Why Learn SQL Over the Summer

Think summer is reserved for flying to warm places and hanging out at the beach? Sure! But it's also a great time to learn new skills that you haven't had time for. If you recently graduated from high school and want to get a head start on computer programming for college, learning SQL over the summer is a great opportunity. You have nothing to lose and everything to gain—SQL is actually really easy to learn, especially with so much free time over the summer.

Here’s Why You Should Learn SQL

Why learn SQL? We asked our users about it. This is what we’ve learned. At LearnSQL.com, we help people with no computer science background to understand the core concepts of databases and data science. For example, we teach users how to extract the most important data from a database to build simple reports and how to understand key statistical metrics in data analysis. We love to provide easy-to-understand examples that thoroughly depict complex technical concepts.

How to Start Thinking in SQL

Thinking in SQL will help you understand what SQL queries do, how to create and change them, and how to create reports from the data you obtain. If you want to know how to write better SQL queries, you have to change the way you think about the code. One of the greatest skills you can have in SQL programming is the ability to change an existing SQL query so you get the results you need.

Introduction to Reporting with SQL — the Ultimate Tutorial for Business Professionals

Working with the financial aspects of large and small enterprises can be a daunting task for a business professional. In this article, we'll look at several ways of constructing the perfect SQL report. You've probably already heard about SQL from your colleagues or in other areas of your career. If you're here, you've likely concluded that learning SQL will make your professional life easier – and you're right!

5 Great Benefits of Learning SQL

If you want your business to succeed in 2017, it’s absolutely critical that you understand your data; this is why you should get acquainted with SQL ASAP. But there are other reasons to learn it that may not be obvious. In this article, I’ll show you 5 huge benefits of learning SQL! Don’t fall for the common trap—analyzing data isn’t just a concern for those competing at national or corporate levels.

Why Is SQL Worth Learning?

Nowadays, data is gathered from a variety of sources, and information is of great value to organizations. However, with an increasing amount of data comes the need for databases that can store information for retrieval and analysis by trained specialists. That’s where Structured Query Language comes in. Is SQL worth learning? In this article, I’ll explain why it definitely is. Relational databases, which logically group information into chunks, are basically used to store and organize large amounts of data.

SQL Mythbuster – 5 Reasons Why No One Should Be Afraid of SQL

Anyone can learn SQL. It’s not as hard as you think! In today’s world, even those in non-technical jobs need some technical skills. And you don’t have to be a hard-core nerd to get these skills. Let me tell you my own story. A few years ago, I wasn’t considering learning SQL or anything else that I labelled “technical”. My background is in sociology, journalism, and scriptwriting, and I thought computer languages were pretty sci-fi.

5 Books That Will Grow Your SQL Skills

Which books will help you build your database skills? We look at five awesome SQL books. There’s a common saying that “all wise men read books”. I would say that all professionals read books – particularly those related to their field. There are many books about databases and SQL; most are tied to specific vendors (DB2, Oracle, MS SQL) but there are also plenty that are vendor-neutral. In this article, I’m going to review a few books that I would recommend to SQL learners at various levels of proficiency.

The Complete Beginner’s Guide to SQL Fundamentals

LearnSQL.com is a great place to learn SQL. If you’re a complete beginner, it’s best to have an overview of what SQL is, what a database is, and how they work together. In this article, you’ll find a complete guide to SQL fundamentals. SQL Fundamentals: Database Let’s begin our guide to SQL with basic definitions. You might have already heard that SQL is used with databases. What exactly is a database?

How to Learn SQL: 6 Ideas for Newbies

Learning a new skill can be a daunting task, especially in programming. SQL is not immune to this. Luckily, with the Internet and the explosion of programming-related information out there, there are a lot of options you can use to undergo your SQL training! But we then come to a new roadblock. Where to begin? How will we know which option is best for our budget, skill level, and schedule?

Tag: Get started with sql

SQL Indexing 101

Indexes are one of the most misused and misunderstood entities in physical database design. A good understanding of indexes and how they solve database performance problems is necessary for any database novice. In this article, we'll look at basic database indexes and their role in database development. To picture what an index is, consider a textbook. At the end of most textbooks is an index listing all the terms one can find in the text and the pages on which they appear.

Tag: Group by

Top 9 SQL GROUP BY Interview Questions

Preparing for an SQL job interview? This guide will walk you through nine basic, intermediate, and advanced GROUP BY questions that you may have to answer. There are common GROUP BY questions that pop up in a lot of SQL job interviews; in this article, we’ll explain how to answer them. If you are a data analyst or another data professional preparing for an interview, this article aims to help you out.

Free Course of the Month – GROUP BY Extensions in PostgreSQL

Do you work with data? Want to be able to create better and more sophisticated SQL reports? Then check out our interactive GROUP BY Extensions in PostgreSQL course. In April 2022, you can complete this online PostgreSQL course for FREE! How can you get this free SQL course in April? Create a free com account or log in if you already have one. Start the course. You will have free access to its content until the end of the month.

How to Include Zero in a COUNT() Aggregate

Explaining how to include zero (0) counts in your SQL query result. Here’s the problem: you want to count something that doesn’t exist, and you want to show your result as zero. How do you do that in SQL? Using the COUNT() aggregate function is a reasonable first step. It will count all the data it finds and return the number of occurrences. But what if there are no occurrences of certain data?

How to Sort Values in a Specific Order in SQL

Sometimes you will be required to order your data in a particular way, and often the use of typical sort modifiers like ASC and DESC are not enough. This article will show you how to use the CASE statement to order your data exactly how you need it to be. Have you ever needed to order your data in a very specific way? One of the best methods for handling complex sorting is using CASE.

Who Has the Highest Salary, Department-wise? Use SQL to Find Out!

This article shows how to get the total salary by department for an organization, using the GROUP BY functionality of SQL. We explain the SQL GROUP BY clause in detail along with conditional filtering using a HAVING clause. Understanding the salary outlay for an organization is one of the common starting points for business leaders. It helps them see who in the organization has the highest total salary cost, department-wise.

What Is the SQL GROUPING SETS Clause, and How Do You Use it?

GROUPING SETS are groups, or sets, of columns by which rows can be grouped together. Instead of writing multiple queries and combining the results with a UNION, you can simply use GROUPING SETS. GROUPING SETS in SQL can be considered an extension of the GROUP BY clause. It allows you to define multiple grouping sets in the same query. Let’s look at its syntax and how it can be equivalent to a GROUP BY with multiple UNION ALL clauses.

What Is the SQL HAVING Clause?

Are you learning SQL? Are you wondering what you can use the HAVING clause for? Or, perhaps, have you tried to use WHERE on your GROUP BY aggregates? You are in the right place! In this article, we explain how to use HAVING with plenty of examples. Have you tried to filter your metrics you created with GROUP BY with a WHERE clause and found out that it did not work?

What Is Advanced SQL?

Are you confused about advanced SQL skills? What are they? This article will explain what advanced SQL can mean, especially as we use it on LearnSQL.com. I’m sure you find the phrases ‘advanced SQL skills’ or ‘advanced SQL topics’ very often. You read one article about advanced SQL and you’re happy with how easy these advanced topics seem to be. Then you talk to someone and you see they consider everything you know as basic SQL knowledge.

Want to Learn GROUP BY Extensions in PostgreSQL? You've Come to the Right Place!

Do you want to take your knowledge of PostgreSQL to the next level? I have something for you: LearnSQL.com’s new GROUP BY Extensions in PostgreSQL course! It will help you get even more out of your data and create better reports and summaries. Fasten your seat belts and prepare to see what GROUP BY can do when it’s turbocharged. First, I have to confess something. I am not objective – I think PostgreSQL is the best and coolest SQL dialect.

What Is GROUP BY in SQL?

GROUP BY is a great SQL feature that allows you to perform powerful calculations on grouped data. Do you want to learn how to get powerful insights from your data? Would you like to know what GROUP BY does and when you should use it? If your answer is yes, keep reading. In this article, you will learn exactly that. Why You Need GROUP BY In today's digitized world – no matter what business you are in – database tables are usually huge, with millions of records.

Why Aren’t SQL Window Functions Allowed in GROUP BY?

It’s true – the SQL order of operations means window functions aren’t allowed in GROUP BY. But you can use them anyway with this special trick. SQL window functions are one of the language’s most powerful features. However, the syntax of window functions is not easy to master. It has lots of details that can cause beginners to stumble. One of the most common traps is trying to use window functions in GROUP BY.

7 Common GROUP BY Errors

Are you making these errors with GROUP BY in SQL? Find out what they are, how to avoid them, and how to fix them. SQL’s GROUP BY statement can quickly uncover powerful data insights. At first, using GROUP BY can seem easy – e.g. when creating basic SQL reports that you’ll present to business decision-makers. But while learning this powerful feature, you could become trapped in weird errors or get incorrect results caused by improperly written GROUP BY statements.

An Overview of Aggregate Functions in SQL

Aggregate functions are commonly used in SQL. This article will lead you through their use and show examples of how they work. SQL aggregate functions are a useful tool, especially for creating reports. They’re not difficult to understand, especially if you have some experience with Excel or similar programs. You’ve probably used aggregate functions like SUM or AVERAGE in a spreadsheet. Even if you only occasionally use them, knowing aggregate functions can help you better understand your data and work more efficiently.

How to Use CASE WHEN With SUM() in SQL

This article will teach you what a CASE WHEN expression is in SQL and how to use it with a SUM() function and a GROUP BY statement. The examples are included to bolster your understanding. Knowing how to use a CASE WHEN expression in SQL adds insight into the exciting possibilities in SQL. It elevates you from a simple user who depends on what SQL returns, to a user who is more in command and who sets specific criteria in SQL.

SQL Course of the Month – GROUP BY Extensions in SQL

Do you want to develop your SQL skills? Do you want to get more out of your data and prepare better reports and summaries? The answer is learning to use SQL’s GROUP BY extensions. But how should you go about this? I asked the same question to Agnieszka Kozubek-Krycuń, Vertabelo’s Chief Content Officer. As she explains, the secret is in this November’s free SQL Course of the Month: GROUP BY Extensions in SQL.

What is the Difference Between COUNT(*), COUNT(1), COUNT(column name), and COUNT(DISTINCT column name)?

Have you noticed there are different variations of the SQL COUNT() function? This article explains the various arguments and their uses. As a SQL user, you’re probably quite familiar with the COUNT() function. Even though it’s relatively simple, it can be used in several different ways. Each way has a very different use. I imagine you’ve seen code that contains the function COUNT(*) or COUNT(1). You’ve probably also seen some other uses of the COUNT() function, such as COUNT(column name) and COUNT(DISTINCT column name), even if you haven’t used them.

How to Fix a 'Not a GROUP BY Expression' Error

Whether you are an experienced SQL user or only a beginner, your SQL queries may return errors. The accompanying messages are supposed to help you fix them; however, sometimes the messages are not very helpful. The Oracle message “Not a GROUP BY expression” is one such example. Let’s review what this is about and how to fix it. We are going to assume some basic understanding of how GROUP BY works.

GROUP BY in SQL Explained

The SQL GROUP BY statement is easy to use, but it can be hard to master. Learn what you can do with GROUP BY, how it works, and how to use it with aggregate functions. GROUP BY is one of the basic SQL tools. However, it might be difficult for beginners to understand how GROUP BY works and how it is used to compute statistics with different aggregate functions. In this article, I’ll use several examples to show exactly how GROUP BY organizes rows and how aggregate functions can be used to calculate statistics on one or more columns.

How to Find Duplicate Values in SQL

Duplicate records waste time, space, and money. Learn how to find and fix duplicate values using SQL’s GROUP BY and HAVING clauses. Database best practices usually dictate having unique constraints (such as the primary key) on a table to prevent the duplication of rows when data is extracted and consolidated. However, you may find yourself working on a dataset with duplicate rows. This could be because of human error, an application bug, or uncleaned data that’s been extracted and merged from external sources, among other things.

How Does SQL GROUP BY Work?

Grouping results is a powerful SQL feature that allows you to compute key statistics for a group of records. GROUP BY is one of SQL’s most powerful clauses. It allows you to see data in a new way and find key metrics (like the average, maximal, and minimal values in a group of records). Without GROUP BY, all the results we obtain are oriented to records. With GROUP BY, we can create groups of records and calculate metrics on each group.

5 Examples of GROUP BY

When you start learning SQL, you quickly come across the GROUP BY clause. Data grouping—or data aggregation—is an important concept in the world of databases. In this article, we’ll demonstrate how you can use the GROUP BY clause in practice. We’ve gathered five GROUP BY examples, from easier to more complex ones so you can see data grouping in a real-life scenario. As a bonus, you’ll also learn a bit about aggregate functions and the HAVING clause.

What Is the Difference Between WHERE and HAVING Clauses in SQL?

As the amount of data in the world grows day by day, the need increases for managing and querying data efficiently. SQL offers ways to manipulate and query data at any scale. As an important part of this, the WHERE and HAVING clauses allow you to filter data as you need, but they are not the same. We will explain the differences between them in detail. One of the most common tasks in manipulating and querying data is filtering using the WHERE and HAVING clauses.

The SQL HAVING Clause Explained

What is the SQL HAVING clause? Why do you need it, and where do you use it? We’ll explain HAVING in detail. HAVING is a very common clause in SQL queries. Like WHERE, it helps filter data; however, HAVING works in a different way. If you are familiar with the GROUP BY clause and have only heard about HAVING – or if you’re not familiar with HAVING at all – this article is what you need.

Using GROUP BY in SQL

Now that you know SQL’s core commands, power up your queries with the GROUP BY clause and aggregate functions. GROUP BY is a SQL clause that arranges data into groups based on a common value (or values). It is widely used to obtain summary information for large datasets as well as for computing basic aggregate statistics. Once you have grasped SQL’s basic commands like SELECT, WHERE, and JOIN, mastering the GROUP BY clause can help you implement your SQL knowledge in real-world business intelligence scenarios.

What Is the Difference Between a GROUP BY and a PARTITION BY?

Window functions are a great addition to SQL, and they can make your life much easier if you know how to use them properly. Today, we will address the differences between a GROUP BY and a PARTITION BY. We’ll start with the very basics and slowly get you to a point where you can keep researching on your own. PARTITION BY vs. GROUP BY The PARTITION BY and the GROUP BY clauses are used frequently in SQL when you need to create a complex report.

Difference between GROUP BY and ORDER BY in Simple Words

For someone who is learning SQL, one of the most common places to get stuck is when learning the GROUP BY command. GROUP BY and ORDER BY are two important keywords in SQL that we use to organize data. The difference between GROUP BY and ORDER BY is that ORDER BY is more simple than GROUP BY and is usually introduced early in an SQL course. Sometimes, people are quite confused over these two concepts (SQL ORDER BY vs.

SQL Hacks To Control Family Budget On Black Friday Weekend

If you’re in the US, chances are you’ve been eagerly awaiting the approach of Black Friday just as much as Thanksgiving. Though the shopping frenzy takes hold of nearly everyone, some people have to stick to their budgets and shop prudently. In this article, we’ll take a look at how generating an SQL report can help you track how much your family spent shopping on Black Friday. Storing Black Friday Purchases in a Database Before we can create an SQL report, we first need some data we can use.

A Beginner’s Guide to SQL Aggregate Functions

Aggregate functions are powerful SQL tools that compute numerical calculations on data, allowing the query to return summarized information about a given column or result set. These functions can be used in conjunction with the GROUP BY statement. Let’s see how they work using some easy examples. SQL Aggregate Functions Suppose we have users residing in a city, and we store their information in two tables. These tables and their relationship are shown below:

Getting the Hang of the GROUP BY Clause

GROUP BY is an important part of the SQL SELECT statement. But new SQL coders can run into some problems when this clause is used incorrectly. Here’s how to avoid those issues. You’re learning SQL. You know how to SELECT some data FROM a table and how to filter the data with a WHERE clause. You can process the data using aggregate functions (MIN, MAX, SUM, AVG, and others). But when you’re dealing with a lot of data, you may need to narrow it down even more.

GROUP BY Clause: How Well Do You Know It?

The database can do different kinds of computations: it can add and subtract, multiply and divide, it can do computations on dates, it can count rows and sum row values, and so on. It can also do quite sophisticated statistics. The GROUP BY clause is the most basic way to compute statistics in SQL. It can be quite tough for beginners but it is really powerful. Let's look at the details of the GROUP BY clause, starting with the basics.

Tag: Guide

How to Install a MySQL Database on a Windows PC

Do you want to install a MySQL database on your Windows computer? And maybe find out how to start using a MySQL database? In this article, we’ll cover the installation process. MySQL is one of the most popular relational database servers. This is one reason to start using a MySQL database. Among the various editions of MySQL delivered by Oracle, the Community edition is available for free. You can download it from the MySQL website.

2021’s Most Popular Databases

What was the most popular database in 2021? And what do you need to know to use it? If you’re learning SQL, you’re in luck. This year’s most popular database uses SQL. But the list doesn’t end there. Read our article and find out the 5 most popular databases this year. My list was based on the latest research of one of the most important platforms in the IT world: Stack Overflow.

SQL Terms Beginners Should Know - Part 4

Here it is – another batch of must-know SQL terms. In the first two parts, we covered tables, relational databases, queries, aliases, SQL JOINs, primary keys, and subqueries. Last time, we moved to more advanced terms like INSERT INTO, GROUP BY, and HAVING. Are you ready to dive deeper into SQL terminology? This is the fourth installment of our series on basic SQL terms for beginners (and everyone else). Don’t worry if you missed the previous articles; you can find Part 1 (essential SQL terms), Part 2, and Part 3 in our blog.

SQL Terms Beginners Should Know - Part 3

This is the third part of my list of essential SQL terms for beginners. In the first, you learned what tables, relational databases, and queries are. In the second part of the tutorial, I told you about aliases, SQL JOINs, primary keys, and subqueries. Now, it's time for more advanced database terms. But don't be afraid! I won’t crush you with scientific definitions. I will explain everything simply so that you can easily understand.

SQL Terms Beginners Should Know – Part 2

This is the second part of my list of essential SQL terms for beginners. In the first, you learned what a table, relational database, and query are. Now, it's time for more advanced database terms. But don't be afraid! I won’t crush you with scientific definitions. I will explain everything simply so that you can easily understand. If you want to review the basic SQL terms, see my previous article, SQL Terms Beginners Should Know.

SQL Terms Beginners Should Know

Have you started learning SQL? Do you feel a little lost in the maze of new words and ideas? Here’s a list of 10 absolutely essential SQL terms for beginners. When you start learning SQL, there’s a lot to process. And some of it – even basic SQL terms – gets lost in the shuffle. If this sounds like you, bookmark this article; it will be a handy reference.

Five Essential Features of a Good SQL Course: What to Look for When Choosing a Course for You

There are many different platforms offering SQL courses. If you’re a beginner, it may be difficult to choose the right one for you. Find out what we think are the essential features of a good SQL course. Remember, if you make a poor choice at the beginning, you may get discouraged or get into bad habits that will impact your work down the line. What Is SQL? SQL, or Structured Query Language, is a programming language you use to talk to databases.

The Most Popular Databases in 2020

Which database solution is currently most popular? Which SQL dialect should you study? In this article, I’ll share the results of my research and my personal experience. Here are the databases that are worth learning SQL to use. First, let's answer some simple questions: Is SQL still useful? Is it worth learning? If you complete an online SQL course, will it make your work easier? The answer is YES! Why?

Top 10 Laptops for Learning SQL in 2020

If you want to learn SQL, you’re going to need a device that’s portable and powerful. I recommend a laptop. Here are the features you’ll need, as well as my picks for laptops to get you learning SQL in 2020! I must admit that browsing Amazon’s computer offers or entering any computer store can give you a headache. So many models, with so many options! They differ in components, workmanship, battery life, and screen size and resolution.

What Is a SQL Dialect, and Which one Should You Learn?

SQL, standard SQL, SQL Server, MySQL, PostgreSQL, Oracle, … You’d like to learn SQL, but you feel overwhelmed with keywords and you don’t know where to start. Let’s explain what each of those terms mean. SQL Is the Language for Talking to Databases A database is a computer program that can store and process large amounts of data. There are many different vendors of databases. PostgreSQL, MySQL, Oracle, and SQL Server are all database products by different vendors.

How to Publish a LearnSQL.com Course Certificate on LinkedIn

LinkedIn draws both job seekers and recruiters. Showcasing your knowledge, skills, and experience on this professional networking site can lead to great opportunities. We know this well at LearnSQL.com. Have you finished one of our courses? Great! Tell your future employer about what you have learned. Here's a step-by-step how-to guide for publishing a course certificate on LinkedIn. I will show you how easy it is to publish a LearnSQL.

Last-Minute Preparation Tips for a Database Class Exam

Getting to learn SQL is fun. You don’t really need to spend much time to understand some basic SQL concepts and use them fluently. If you’re a student facing your first database class exam soon, we’ve got you covered. In this article, we explain what you should focus on while learning SQL and studying for an entry-level database exam. Check your knowledge with our 10 sample questions and discover where you can find more SQL practice.

Top 5 Programming Languages to Learn Alongside SQL

If you already know or are about to learn SQL, you’re well on your way to being a sought-after database administrator, database engineer, or just a general database whizz kid! SQL is a modern, widely-used language that finds application in almost every industry. There is no shortage of jobs with SQL. But what if you want to branch out and learn another language to complement your SQL knowledge and skills?

Advanced SQL Courses for Data Analysts – A Complete Review

Even data analysts who already know SQL need to keep their skills sharp. Where can you find the best advanced SQL courses for data analysts? Check out our review of the top online sources! In this article, I present a list of online SQL courses for data analysts. These courses are offered by various platforms. Why wait? Let’s jump right in! 8 Advanced SQL Courses for Data Analysts Let's take a closer look at these courses to decide which platform will be better for you in learning SQL.

What SQL Practice Do You Need to Prepare for a Technical Job Interview?

You’ve scored yourself an interview for an SQL-related job. Nice work! But perhaps uncertainty is creeping in as your interview date looms closer. Do you know enough SQL to make the cut? What questions are you likely to be asked? What SQL practice should you be doing before your interview? Almost all SQL job candidates go through exactly the same nerve-wracking process. Here at LearnSQL.com, we have the lowdown on all the SQL practice and preparation you’ll need to ace those interview questions and take your career to the next level.

Is SQL Worth Learning?

We’re in the 21st century. These are the “ultimate data times” in which loads of information on all kinds of things is available. We want to explore this info even more, slice and dice it, understand where it comes from and what triggers it. With such large amounts of data coming in, people have discovered that spreadsheets aren’t enough. There’s a need for a greater solution, something like a spreadsheet on steroids.

Top 3 Platforms to Learn SQL Online: A Complete Comparison

Do you want to learn SQL online? Where do you start? There are many choices on the internet, and it can be hard to decide. But don’t worry—I tested and compared three major platforms to help you find the best place to learn SQL online! E-learning is on the rise. It gives us infinite possibilities of growing our professional careers without leaving our homes. And increasing our competencies is especially important now that the labor market has become dynamic and unstable.

Choose the Best Way to Learn SQL

SQL has become a hot topic in the professional world, and many resources have appeared both online and offline for learning SQL. It’s easy to get lost in the jungle of books, tutorials, and courses. Which resources do you choose? If you want to know how to learn SQL quickly and effectively, take a look at my list. There are many reasons for learning SQL. We asked our users about them and learned that there was no universal motive.

50 Best Resources for Learning SQL

Do you want to know where to learn SQL? We’ve got you covered with the ultimate list of 50 resources for learning SQL, including the best SQL courses, tutorials, books, and much, much more! Learning SQL can be hard enough without wading through thousands of websites and articles. So, we thought we’d do you a solid and put the top SQL resources here in this handy slice of the internet.

How to Stay Healthy When Learning SQL

So, maybe you’re learning SQL. Congratulations! Or maybe you already work as a data analyst, DBA, or data scientist. That’s great too! Either way, you are most likely spending hours in front of a computer. I will give you tips on how to avoid bad habits and take care of your health while learning and/or working with SQL. Have you ever wondered how sitting in front of a computer affects your health?

What Programming Language Should You Learn?

If you've ever been wondering which programming language you should learn first, you know that's a tough nut to crack. It’s especially difficult if you are new to IT and programming. In this article, I give suggestions for what to learn first and what perspectives each language can give you in IT. There are hundreds of programming languages, and new ones are showing up all the time. Getting to know all of them is simply impractical and impossible.

How to Study Online: 5 Steps to Becoming an Effective Learner

If you suffer from procrastination or lack of motivation, you’re not alone. We have some online learning tips to make your learning journey smoother and more enjoyable. One of the best things about being an adult is that we can do what we want: go to sleep late at night, party until morning, eat junk food. Besides all those small pleasures, as adults we are responsible for ourselves, our choices, and our mistakes.

How to Install PostgreSQL on Windows 10 in 5 Minutes

It may look like a complicated task to install PostgreSQL, Oracle, or SQL Server or any other database software, but it really isn’t! These days, most relational database management systems come with installation wizards that make the process much simpler. In this article, we’ll look at how to install PostgreSQL and test that the installation is working. Install PostgreSQL: Steps Involved To install PostgreSQL, we’ll complete the following tasks:

Tag: Having

What Is the SQL HAVING Clause?

Are you learning SQL? Are you wondering what you can use the HAVING clause for? Or, perhaps, have you tried to use WHERE on your GROUP BY aggregates? You are in the right place! In this article, we explain how to use HAVING with plenty of examples. Have you tried to filter your metrics you created with GROUP BY with a WHERE clause and found out that it did not work?

SQL HAVING Tutorial

Learn how to use the SQL HAVING clause to filter groups using your own specified conditions. The SQL HAVING clause is often a challenging concept to grasp, especially for beginners. Additionally, its specific use cases can be difficult to visualize without specific examples based on real-world datasets. In this tutorial, you will learn how to apply the SQL HAVING clause to filter groups of records based on specified conditions. You’ll see examples where we apply this concept to solving business problems on a realistic dataset.

HAVING vs. WHERE in SQL: What You Should Know

This article is about SQL’s WHERE and HAVING clauses. Both clauses are part of the foundations of the SQL SELECT command. They have similar uses, but there are also important differences that every person who uses SQL should know. Let’s see what’s behind the HAVING vs. WHERE debate. In this article, we’ll suppose we work for a government social agency supporting people or families whose income is below a certain threshold.

Tag: Health

How to Stay Healthy When Learning SQL

So, maybe you’re learning SQL. Congratulations! Or maybe you already work as a data analyst, DBA, or data scientist. That’s great too! Either way, you are most likely spending hours in front of a computer. I will give you tips on how to avoid bad habits and take care of your health while learning and/or working with SQL. Have you ever wondered how sitting in front of a computer affects your health?

Tag: Hierarchical data

Hierarchical Data and How to Query It in SQL

How do you recognize hierarchical data, and how do you query it? Two common SQL questions are about to be answered. Querying hierarchical data is a rather common situation if you’re working with SQL and relational databases. Not that hierarchical data is something mystical and rare; on the contrary, it’s everywhere. So why is hierarchical data so challenging when it comes to relational databases? Mainly, the difficulties occur in translating hierarchical data to relational database principles.

Tag: How to

Practical Ways to Improve the Performance of SQL Queries

Knowing how to improve SQL query performance is an important skill, especially when working with with large databases. In this article, you'll learn how to write more efficient SQL queries to get results faster. The biggest difference between SQL and other languages is that SQL is a non-procedural language. In a non-procedural language you specify the results that you need but not the methods used to get it. The advantage of a non-procedural language is that it is easier to write programs, therefore it is common for non-programmer business users to generate reports from SQL queries.

SQL Filtering 101

Sometimes, SQL queries return lots of data you don't need. In this article, we'll look at a simple example of filtering SQL queries to reduce the complexity of your data. The key to learning how to filter data in SQL is understanding the very basics of Boolean algebra. That's just a fancy term mathematicians use to describe expressions involving logical values (true/false) and their associated operators (and, or, not, etc.

Improving Query Readability with Common Table Expressions

What is a Common Table Expression, or CTE? Where do you use them, and why? This post answers your questions. Simply put, Common Table Expressions (also known as WITH clauses) are essentially named subqueries. They also provide additional features like recursion. If you're new to subqueries, I recommend you read the SQL Subqueries article before continuing. The main purpose of Common Table Expressions is to improve the design and readability of an SQL statement.

SQL Development? Structured Query Language and Apps

You know about using SQL with databases. How does SQL fit in with app development? Is there anything like SQL development? In this post, we look at the app development process, how it intersects with modeling a database, and what developers can do with SQL outside of their app. Obviously, the beginning of this process is defining your app — what it does, who it is for, how it will function and look, etc.

Performing Calculations on Date- and Time-Related Values

Relational databases support several date and time data types. In this article, we'll look at several arithmetic operations we can do on these types. These operations are logical and understandable, even for the beginning SQL coder. Let's first briefly explain the main data types used for dates and times. Keep in mind that data types may differ by database engine, so check your database documentation for specifics before you start working with them.

Getting the Hang of the GROUP BY Clause

GROUP BY is an important part of the SQL SELECT statement. But new SQL coders can run into some problems when this clause is used incorrectly. Here’s how to avoid those issues. You’re learning SQL. You know how to SELECT some data FROM a table and how to filter the data with a WHERE clause. You can process the data using aggregate functions (MIN, MAX, SUM, AVG, and others). But when you’re dealing with a lot of data, you may need to narrow it down even more.

Refine Results with SQL Set Operators

Using UNION, UNION ALL, EXCEPT, and INTERSECT to manage SQL query results. The function of SQL set operators is pretty simple; they allow us to combine results from different SQL queries into one result set. The best way to understand how set operators work is to use visual methods like the Venn diagram. For those of you not familiar with Venn diagrams, they are two circles that represent items or collections of items.

6 Common SQL Syntax Mistakes All Learners Make

We all make mistakes when learning a new language – especially at the beginning. New words, complicated grammar... Everyone needs time to master a language. But when we get immediate feedback, we can progress more quickly. The same goes for learning SQL. In this article, we'll look at 6 common SQL syntax mistakes most SQL learners make. Mastering SQL Queries Interactive SQL courses are one way to get immediate feedback on your queries.

8 Tips Absolute Beginners Can Use to Fix SQL Queries

Code errors are common – and frustrating. And when you're just learning SQL, it can be very challenging to find and fix your mistakes. In this post, we'll show you eight ways to solve or eliminate common SQL coding errors. Today, we'll talk about some tips the SQL beginner can use to avoid several common errors. These tips work in any database environment. As we go along, we'll be showing some error messages.

Five Common SQL Syntax Errors

As you learn SQL, watch out for these common coding mistakes You’ve written some SQL code and you’re ready to query your database. You input the code and …. no data is returned. Instead, you get an error message. Don’t despair! Coding mistakes are common in any programming language, and SQL is no exception. In this post, we’ll discuss five common SQL syntax errors people make when writing code.

SQL Errors: Five Common SQL Mistakes

As you learn SQL, watch out for these common coding mistakes You’ve written some SQL code and you’re ready to query your database. You input the code and …. no data is returned. Instead, you get an error message. Don’t despair! Coding errors are common in any programming language, and SQL is no exception. In this article, we’ll discuss five common mistakes people make when writing SQL. The best way to prevent mistakes in SQL is practice.

Tag: How to in sql

Practical Ways to Improve the Performance of SQL Queries

Knowing how to improve SQL query performance is an important skill, especially when working with with large databases. In this article, you'll learn how to write more efficient SQL queries to get results faster. The biggest difference between SQL and other languages is that SQL is a non-procedural language. In a non-procedural language you specify the results that you need but not the methods used to get it. The advantage of a non-procedural language is that it is easier to write programs, therefore it is common for non-programmer business users to generate reports from SQL queries.

How to Begin Running SQL Queries

In this article, I’ll explain how to run a SQL query to help you execute your first one. Let’s jump right in! Running SQL queries for the first time is not a complex task, but it can seem intimidating at first if you’re a complete beginner. But once you get past that initial roadblock, you’ll be able to focus on learning SQL and writing more interesting queries to meet your business needs.

SQL Indexing 101

Indexes are one of the most misused and misunderstood entities in physical database design. A good understanding of indexes and how they solve database performance problems is necessary for any database novice. In this article, we'll look at basic database indexes and their role in database development. To picture what an index is, consider a textbook. At the end of most textbooks is an index listing all the terms one can find in the text and the pages on which they appear.

How to Use a SQL Wildcard

SQL wildcard allows us to filter data matching certain patterns in SQL. We use SQL wildcards with the LIKE operator in the WHERE clause of a query to filter data. In this beginner’s article, we’ll look at everything you need to know about basic SQL wildcards. If you like playing cards, then you know that wildcards can substitute any other card in your deck. Similarly, SQL wildcards can substitute one or more characters.

SQL Filtering 101

Sometimes, SQL queries return lots of data you don't need. In this article, we'll look at a simple example of filtering SQL queries to reduce the complexity of your data. The key to learning how to filter data in SQL is understanding the very basics of Boolean algebra. That's just a fancy term mathematicians use to describe expressions involving logical values (true/false) and their associated operators (and, or, not, etc.

Why Learn SQL Over the Summer

Think summer is reserved for flying to warm places and hanging out at the beach? Sure! But it's also a great time to learn new skills that you haven't had time for. If you recently graduated from high school and want to get a head start on computer programming for college, learning SQL over the summer is a great opportunity. You have nothing to lose and everything to gain—SQL is actually really easy to learn, especially with so much free time over the summer.

Key Insights for Mastering SQL Queries Using Tinder Data Example

Going from zero to one can be daunting in any endeavor. The same is true for learning new programming languages, even simple ones like SQL. In this article, we’ll take a look at some key insights that will help you understand the nuances of mastering SQL queries. If you’ve never used SQL, you’re in the right place. When learning anything new, you’ll find that there are always some key insights or tips that can help you on your way.

Improving Slow Query Performance: When Runtime Matters

As SQL users, we usually focus on writing queries that return correct results. However, there are more things to consider when you're writing a query; one of them is query performance. In this article, we'll look at some examples where query response time is critical. Scene One: 911 Call Center Let's suppose we're at a 911 call center, when the phone rings. One of the operators answers the call; a witness reports that a man has been shot.

Converting Subqueries to Joins

Not all queries are alike, especially in terms of performance. In this article, we'll look at how you can convert SQL subqueries to joins for improved efficiency. When should I use SQL subqueries? Great question! Unfortunately, there's no concrete answer. SQL beginners tend to overuse subqueries. Typically, once they find that SQL construction works in one situation, they try to apply that same approach to other situations. It's only natural.

Essential SQL Terms to Know for Beginners and Pros

Working with databases can seem daunting to a non-technical person. Right away, you’re bombarded with new terms that make your head spin. Database, database instance, table, SQL and others are some of the basic terms that you need to understand just to have a normal conversation with your technical colleagues. In this article, we’ll explore some basic SQL database terminology you need to know to succeed. Imagine you’re attending a meeting with the development staff and suddenly feel as if you’re listening to white noise.

Learn to Write a SQL Correlated Subquery in 5 Minutes

If you’re familiar with the famous Russian nesting doll, then SQL correlated subqueries should be a peace of cake to understand—subqueries are just queries nested within queries. An SQL subquery is often called an “inner” query; the main query is usually called the “outer” query. This article covers everything you need to know about correlated subqueries. What Exactly is a SQL Correlated Subquery? A correlated SQL subquery is just a subquery that is executed many times—once for each record (row) returned by the outer (main) query.

New LearnSQL.com Online Practice – Solve Basic SQL Questions with the SQL Practice Set

If you’re looking to retrieve any kind of information from a database, you need to speak its language. But querying databases is an art—and it demands practice. That’s why we created our SQL practice set: a pack of SQL online practice exercises meant to help you master your skills. We spend a lot of time not only developing new courses but also speaking with our users and learning what they expect from SQL online practice exercises.

How to Become a Database Analyst

Curious about becoming a database analyst? Maybe you've taken some database courses at university and they really struck a chord. Or maybe you learned online. Now you're thinking about making a career out of working with databases. Where would you start? What should you expect at each phase of your professional development? In this post, we'll explore the challenging and exciting world of databases analysis. We'll go from the very beginning of a career to the apex of professional success.

Extracting Data From a String: SPLIT_PART in PostgreSQL

Learn how to use split_part in PostgreSQL to extract data from strings. Quite often, we’d like to extract parts of a string when working with text values. A common example is when we have a full name and need to retrieve only the last name. In this article, we’ll examine how to do it using split_part in PostgreSQL, i.e. a string-related function that can be used to extract a substring.

How to Remove Junk Characters in SQL

Unwanted characters in text data can be a bit of a pain, but there’s an easy way to fix them. Scroll down to learn how to remove junk characters in SQL in the easiest way! Sometimes, we’ll find unwanted characters inside our string data because our SQL queries didn’t work as expected. Moreover, these extra characters may sometimes be invisible, which really complicates things. In this article, we’ll examine some string-related SQL functions that can handle unwanted characters—visible or not!

How to Solve Capitalization Data Quality Issues

Misspelled names, typos, and text data quality issues in your database? Power up your queries! Use SQL string functions to address data quality issues related to capitalization. Sometimes, our SQL queries don't work as expected because of data quality issues. In this article, we will examine some string-related SQL functions that can correct data quality issues related to capitalization. We'll be using PostgreSQL in our examples, but similar functions are available in most database engines.

18 Useful Important SQL Functions to Learn ASAP

Beginning with SQL: Useful Functions to Master Learning a new programming language can seem intimidating. Like any other language, a programming language has a large vocabulary that you need to master. In this article, we'll look at some of the most useful SQL functions that you need to know. There are many useful SQL functions for working with different data types. Once you practice with some of the most common ones, you'll gain enough confidence to move on to more advanced material.

Simplify SQL Code: Recursive Queries in DBMS

Hey SQL users! Are you repeating the same query in every report? Are your queries getting too complicated? Use recursive queries to simplify SQL code! Too many SQL reports can lead to clutter on your desktop and in your head. And is it really necessary to code each of them separately? Ad-hoc queries can share much of the same SQL code with managerial reports and even regulatory reports. Suppose you’ve been writing basic SQL code for a while.

Digging Into Data: Explore and Analyze Survey Results With SQL

Excel is a powerful beast that lets you analyze complex data. Yet, operating on big chunks of data can sometimes be a daunting task. Let's take a look at how SQL can help. Today, we'll tackle a common problem with importing data to an SQL database, using a real-life example. Suppose your company conducted a survey on the most popular programming trends and preferences, striving to meet the expectations of its users.

SQL Hacks To Control Family Budget On Black Friday Weekend

If you’re in the US, chances are you’ve been eagerly awaiting the approach of Black Friday just as much as Thanksgiving. Though the shopping frenzy takes hold of nearly everyone, some people have to stick to their budgets and shop prudently. In this article, we’ll take a look at how generating an SQL report can help you track how much your family spent shopping on Black Friday. Storing Black Friday Purchases in a Database Before we can create an SQL report, we first need some data we can use.

SQL Window Functions By Explanation

In our previous post, we explained how SQL window functions work by example. We started with some very simple, basic functions. Let's extend it by explaining subclauses in window functions. SQL window functions are a great way to compute results from a set of rows rather than a single row. As you know from our first article, the "window" in window function refers to the set of rows. We showed you some examples of simple window functions like RANK and LEAD.

The 5 Highest Paying Jobs That Use SQL

IT provides a wide and growing job market, offering many excellent opportunities in both career development and earning potential. Today we’ll take a look at several very interesting types of database jobs that use SQL. Every year, many in the work force set their sights and aim for new and better jobs. When it comes to jobs, “better” means different things to different people, but earning potential is almost always a top priority.

Four Reasons You Must Learn SQL in Data Science

Is SQL important for data science? It certainly is! This language can help you build a foundation for your analytical career. Let’s see how you use SQL in data science. Data science is hot right now. What if you could predict the next market crash? Or contain the spread of Ebola? Or accurately predict a health crisis months or even years before it happens? Data scientists are working hard on these kinds of projects, and they are earning healthy salaries in the process.

SQL Mythbuster – 5 Reasons Why No One Should Be Afraid of SQL

Anyone can learn SQL. It’s not as hard as you think! In today’s world, even those in non-technical jobs need some technical skills. And you don’t have to be a hard-core nerd to get these skills. Let me tell you my own story. A few years ago, I wasn’t considering learning SQL or anything else that I labelled “technical”. My background is in sociology, journalism, and scriptwriting, and I thought computer languages were pretty sci-fi.

Introducing SQL Set Operators: Union, Union All, Minus, and Intersect

Ever heard terms such as union and intersection in SQL? They're examples of set operators, and they come in handy when you need to combine information from multiple tables or queries. In this article, we'll take a closer look at them. SQL queries let us choose the most important bits from large amounts of information. Of course, we can't expect that all necessary data will be stored in one table.

Improving Query Readability with Common Table Expressions

What is a Common Table Expression, or CTE? Where do you use them, and why? This post answers your questions. Simply put, Common Table Expressions (also known as WITH clauses) are essentially named subqueries. They also provide additional features like recursion. If you're new to subqueries, I recommend you read the SQL Subqueries article before continuing. The main purpose of Common Table Expressions is to improve the design and readability of an SQL statement.

Complete SQL Practice for Interviews

Congratulations! Your SQL skills were strong enough to get you that job interview! Now, if you only knew what SQL questions and practical exercises a recruiter might ask you to do… This article is meant as a SQL practice for interviews. I’ll help you prepare for the SQL and database aspects of your job interview. In a previous article, I explained how can you boost your career by learning SQL.

SQL Development? Structured Query Language and Apps

You know about using SQL with databases. How does SQL fit in with app development? Is there anything like SQL development? In this post, we look at the app development process, how it intersects with modeling a database, and what developers can do with SQL outside of their app. Obviously, the beginning of this process is defining your app — what it does, who it is for, how it will function and look, etc.

The Complete Beginner’s Guide to SQL Fundamentals

LearnSQL.com is a great place to learn SQL. If you’re a complete beginner, it’s best to have an overview of what SQL is, what a database is, and how they work together. In this article, you’ll find a complete guide to SQL fundamentals. SQL Fundamentals: Database Let’s begin our guide to SQL with basic definitions. You might have already heard that SQL is used with databases. What exactly is a database?

Performing Calculations on Date- and Time-Related Values

Relational databases support several date and time data types. In this article, we'll look at several arithmetic operations we can do on these types. These operations are logical and understandable, even for the beginning SQL coder. Let's first briefly explain the main data types used for dates and times. Keep in mind that data types may differ by database engine, so check your database documentation for specifics before you start working with them.

Getting the Hang of the GROUP BY Clause

GROUP BY is an important part of the SQL SELECT statement. But new SQL coders can run into some problems when this clause is used incorrectly. Here’s how to avoid those issues. You’re learning SQL. You know how to SELECT some data FROM a table and how to filter the data with a WHERE clause. You can process the data using aggregate functions (MIN, MAX, SUM, AVG, and others). But when you’re dealing with a lot of data, you may need to narrow it down even more.

Refine Results with SQL Set Operators

Using UNION, UNION ALL, EXCEPT, and INTERSECT to manage SQL query results. The function of SQL set operators is pretty simple; they allow us to combine results from different SQL queries into one result set. The best way to understand how set operators work is to use visual methods like the Venn diagram. For those of you not familiar with Venn diagrams, they are two circles that represent items or collections of items.

6 Common SQL Syntax Mistakes All Learners Make

We all make mistakes when learning a new language – especially at the beginning. New words, complicated grammar... Everyone needs time to master a language. But when we get immediate feedback, we can progress more quickly. The same goes for learning SQL. In this article, we'll look at 6 common SQL syntax mistakes most SQL learners make. Mastering SQL Queries Interactive SQL courses are one way to get immediate feedback on your queries.

8 Tips Absolute Beginners Can Use to Fix SQL Queries

Code errors are common – and frustrating. And when you're just learning SQL, it can be very challenging to find and fix your mistakes. In this post, we'll show you eight ways to solve or eliminate common SQL coding errors. Today, we'll talk about some tips the SQL beginner can use to avoid several common errors. These tips work in any database environment. As we go along, we'll be showing some error messages.

How to Learn SQL: 6 Ideas for Newbies

Learning a new skill can be a daunting task, especially in programming. SQL is not immune to this. Luckily, with the Internet and the explosion of programming-related information out there, there are a lot of options you can use to undergo your SQL training! But we then come to a new roadblock. Where to begin? How will we know which option is best for our budget, skill level, and schedule?

Five Common SQL Syntax Errors

As you learn SQL, watch out for these common coding mistakes You’ve written some SQL code and you’re ready to query your database. You input the code and …. no data is returned. Instead, you get an error message. Don’t despair! Coding mistakes are common in any programming language, and SQL is no exception. In this post, we’ll discuss five common SQL syntax errors people make when writing code.

SQL Errors: Five Common SQL Mistakes

As you learn SQL, watch out for these common coding mistakes You’ve written some SQL code and you’re ready to query your database. You input the code and …. no data is returned. Instead, you get an error message. Don’t despair! Coding errors are common in any programming language, and SQL is no exception. In this article, we’ll discuss five common mistakes people make when writing SQL. The best way to prevent mistakes in SQL is practice.

Tag: Ide

Best SQL IDEs for You in 2021

Maybe you just started learning SQL. Maybe you already have some experience. Whatever your situation is, choosing the right IDE for you is another step in your development. Why IDE? IDE stands for integrated development environment. It is a software application that enables us to combine various aspects of writing a computer program. An IDE usually contains a source code editor, build automation tools, and a debugger. You might ask why you need an IDE when you have the command line available on your computer.

Tag: Insert

What Is the INSERT Statement in SQL?

The INSERT statement in SQL is used to add new data to your database. This article will explain how to use it and show you practical examples along the way. When you learn SQL, you focus on getting data out of a database, working mostly with SELECT. In SQL, there are also statements that let you modify data in a database. The first one is the INSERT statement: it adds data to a table.

Learn SQL Views in 30 Minutes

Views aren't complicated – if you've got half an hour, we'll get you started writing SQL queries using views! Let's start by answering the question "What is a view in SQL?'. A view is a database object (as is a table, an index, or a stored procedure). Like a table, you can query a view and extract the information in it. It can be used in the FROM clause of a SELECT, and you can reference view columns in clauses like SELECT, WHERE and GROUP BY among other clauses as well.

Using CASE with Data Modifying Statements

What happens when you combine CASE with SQL's data modifying statements? Find out in this article. The CASE expression is a very useful part of SQL and one that you'll employ frequently. We've already covered what the CASE expression does, how to format it, and how to use it in a SELECT statement in "Using CASE to Add Logic to a SELECT". Another article, "How to Sort Records with the ORDER BY Clause"

Tag: Installation guide

How to Install Microsoft SQL Server 2019 and SQL Server Management Studio

Do you want to install SQL Server 2019 on your Windows PC? How about the latest version of SQL Server Management Studio? I’ll walk you through the process. Soon you’ll be writing T-SQL queries and operating on SQL Server databases! As I write this article, Microsoft SQL Server 2019 is the latest version of SQL Server. It’s the 15th version of one of the most popular database servers in the world.

Microsoft SQL Server 2017 Installation Step by Step

Microsoft SQL Server is one of the most popular professional database servers on the market. In this guide, I’ll show you all SQL Server 2017 installation steps to help you install it on the Windows operating system together with SQL Management Studio. If you want to learn T-SQL, the dialect of SQL used in SQL Server, check out our SQL from A to Z in MS SQL Server track.

How to Begin Running SQL Queries

In this article, I’ll explain how to run a SQL query to help you execute your first one. Let’s jump right in! Running SQL queries for the first time is not a complex task, but it can seem intimidating at first if you’re a complete beginner. But once you get past that initial roadblock, you’ll be able to focus on learning SQL and writing more interesting queries to meet your business needs.

Tag: Intersect

What Do the SQL INTERSECT and MINUS Clauses Do?

Do you know the difference between SQL’s INTERSECT and MINUS clauses and how to use them? You will find examples and explanations in this article. SQL INTERSECT and MINUS are useful clauses for quickly finding the difference between two tables and finding the rows they share. INTERSECT compares the data between tables and returns only the rows of data that exist in both tables. MINUS compares the data between tables and returns the rows of data that exist only in the first table you specify.

Tag: Jobs and career

Top 10 MySQL Interview Questions And Answers

You learned SQL and now you want to use this valuable skill to get a better job. Now it’s time to prepare for the job interview. We’ve got ten MySQL interview questions and answers to help you with that. In today's hyperconnected world, knowing how to deal with it has become a necessary skill. That’s why you probably learned (or want to learn) SQL: either your job requires it or you realized that you need SQL to get a better job.

Prepare for a SQL Interview with LearnSQL.com

You've been working hard to get a SQL interview at your dream company. Now they’ve called – and you need to prepare if you’re going to ace it. In this article, I’ll show you the most efficient way to prepare for a job interview using the interactive SQL courses at LearnSQL.com. SQL is an essential skill for anyone working with data. Wanna be a data analyst, data scientist, software engineer, or tester?

5 Tips for You From a Senior SQL Data Analyst

Are you looking for tips for becoming a better data analyst? Do you want to know about the mistakes and issues you may face? I have collected five tips for your everyday work based on my experience as a data analyst. You may have already read about what data analysts do, how much they earn, and how to become one. However, there is more to it than just becoming a data analyst.

Top 9 SQL GROUP BY Interview Questions

Preparing for an SQL job interview? This guide will walk you through nine basic, intermediate, and advanced GROUP BY questions that you may have to answer. There are common GROUP BY questions that pop up in a lot of SQL job interviews; in this article, we’ll explain how to answer them. If you are a data analyst or another data professional preparing for an interview, this article aims to help you out.

PostgreSQL Interview Questions and Answers

Job interviews are always stressful. Interviewing and getting asked technical questions about PostgreSQL is even more of a challenge! In this article, we’ll cover some of the PostgreSQL interview questions you can expect when applying for a new job. By the end of the article, you should be able to handle most of the questions you are likely to face. We’ve previously covered common questions you can expect at a SQL job interview, but this article will be focused on Postgres specifically.

Top 5 SQL CTE Interview Questions

Here are five questions (and solutions!) on CTEs you’ll (probably) be asked at an interview. I’m not saying you will get these SQL CTE interview questions at every job interview. But when you do, they are probably along the lines of the five I’m about to show here. Other than theoretical questions about CTEs, there are not that many variations in the CTE scenarios evaluated by interviewers. Go through these five examples, and you get a good foundation for acing your interview!

SQL for Startups – Do You Need It?

If you’ve been wondering whether to use SQL in your startup, it’s probably high time to do so. SQL can be an amazing tool for small, fast-growing businesses. But don’t worry if you’re unfamiliar with SQL for startups. Maybe you are not sure what SQL is all about. Don’t worry; you don’t have to make any decisions this second! First, answer these questions: Can you think of any data related to your business – prices, clients, details about clients, production details, budget, costs, strategy, or anything else?

How SQL Helps Everyone in Your Office

I don't know about you, but I really like to make my life easier. If something can be done faster and more efficiently, especially if it's everyday, routine tasks, I’m all for it! This is where SQL works brilliantly. It's not just about complicated data analysis. Everyone in the office works with different types of data, and SQL can help anyone. How? Anything is possible once you learn SQL!

How to Show Your Sql Experience

Do you want to work in the IT industry? This is now one of the best ideas for a good career. What should convince you to do so? Demand for specialists, high earnings, and the fact that it is a future-proof profession. Interestingly, it's not gonna be that hard – especially for you, smartie! You just need some skills and good preparation for an interview to be successful. I'll tell you how to land a great job!

How Much Do Data Analysts Earn in 2021?

How Much Do Data Analysts Earn in 2021? How much does a data analyst earn? We did some data analysis ourselves. Nothing fancy, but it will give you some extra motivation for learning SQL for your data analyst gig. Data, data everywhere! We live in the world of (big) data. Having data is just the first step. Knowing what to do with it, how to interpret it, and what insights it holds, is true greatness.

How Will a SQL Course Improve the New Employee Onboarding Process?

Are you looking for something to improve the onboarding process of new employees at your company? If they will be working with databases and SQL, and if you need resources for them to learn quickly, choose interactive SQL online courses. You’ve just hired some new employees. Great! After a long recruitment process, you have finally managed to find people who can do the job and meet your expectations. You may have even used our advice on why it makes sense to Practice SQL Before Interviewing a Potential Employee.

Top 10 SQL Window Functions Interview Questions

Many interesting job positions require SQL skills – and that includes window functions, which are not commonly taught in online courses. In this article, I will cover the top window function questions for every experience level. If you’re going for a job interview for an advanced SQL position or for intermediate to advanced data analyst positions, you’ll probably be asked about your knowledge of SQL window functions. Don’t panic! Although these functions aren’t commonly covered in online courses, we’ve got the answers right here.

Best SQL Certifications for Leveling up Your Career

Career If you want to build and strengthen your position in the IT industry, you should look into these SQL certifications. We always encourage you to learn, to gather new skills and experience. Training is really important; without it, you will not make much progress if you want to advance in IT or specifically in the SQL industry. That said, you also need something that can validate your competencies, like SQL certifications.

Top 15 SQL Interview Questions in 2021

If you are on the lookout for a job in the field of data, you’re almost guaranteed to face SQL interview questions. You might even be asked to complete some kind of SQL coding test. According to KDnuggets, irrespective of the specific role in data – data analyst, data engineer, data scientist, or business intelligence analyst – SQL lands in the top three skills found in postings across Indeed, SimplyHired, and Monster.

Skills Every Data Analyst Should Have

If you’re a student looking for career advice or a specialist seeking new job opportunities, find out if a data analyst job is something worth considering. In today's article, I explain the essential skills required for data analysts and benefits that come from performing such a job. What Is a Data Analyst? Let’s start by defining exactly what a data analyst is. A data analyst is someone who uses their skills to collect, analyze, and report insights from company data.

Where Can I Find a Data Analyst Internship?

Are you wondering how to land a data analyst job without any professional experience? This article is the answer! Finding an SQL-related internship – an important part of eventually landing a data analyst job. Internships enrich your CV and, more importantly, help you learn SQL from the practical side. I will tell you where to find data analyst internships and what you should know about them. That's right! To gain experience, you need experience – especially when you’re entering the labor market or embarking on a new career.

Want to Work With Data? Learn SQL!

Are you looking for a database job? How are things working out? If you don't know what to do, I suggest you start by learning SQL. Here’s why. In this article, I’ll explain how you can succeed at finding a database job. If you are tired of your current job and fed up with your boss (who hasn't given you a raise in years), read on. Stay with me too if one more stupid Zoom call will make you scream.

Practicing SQL for Your First Day of Work

Your new SQL job is likely to surprise you in many ways. To minimize the risk of getting lost in the jungle of data, I recommend you get some additional SQL practice before your first day. There are special SQL practice sets and projects on the internet to help you prepare. You’ll also get help from your colleagues, as programmers are usually open and supportive. If you’re reading this, you’ve probably heard about the opportunities SQL and data science offer.

The Top 10 SQL JOIN Interview Questions and How to Answer Them

Have you ever wondered what SQL JOIN questions you might be asked in an interview? Do you feel prepared to answer them? This article covers the most common SQL JOIN interview questions and how to answer them. If you are applying for a job as a data analyst or software developer, you will likely be asked about your SQL JOIN knowledge. SQL JOIN clauses are a great topic for interviewers to quiz you on.

Practice SQL Before Interviewing a Potential Employee

Has your company grown to the point that you need to hire an SQL expert? Have you found a candidate for the job? How do you prepare for the interview, especially if you don’t know SQL? Don't worry! Follow our suggestions on how to practice SQL. We have tips and tricks to help you feel confident and find the perfect employee. Who You Want To Hire First of all, you need to know the requirements for the new employee.

How to Boost Your Company With SQL Courses

SQL has the power to supercharge the capabilities and performance of your entire company. But if you don’t dip your toes in the water and give some SQL courses a go, you’ll never realize the vast potential of the language. SQL, or Structured Query Language, is your ticket to expanding the scope and the results of your business or organization, no matter what sector you operate in. Whether you’re the owner or manager of your company or simply an employee interested in improving operations, learning SQL is undoubtedly, unquestionably, for you.

How Will Learning SQL Make You a Better Boss?

Want to improve the performance of your team, of your own, of your department, or of your entire company? Try SQL! Why should you learn SQL? Because it just pays off! What does learning SQL and being a better boss have to do with each other? Being a better manager can make your employees happier while growing your business. When employees feel a sense of fulfillment, they are more motivated to do well.

How Much Do Data Engineers Earn in 2020?

Data engineering is a hot job right now. What does a data engineer do? And just how much do they earn? We’ve done the research for you. If you are reading this, you’re either starting to learn SQL or you already know some and feel it’s time to look around for a SQL job. Maybe you’re in the midst of tackling our Creating Database Structure track. And, let’s be honest, maybe you need some extra motivation to keep on you track.

Why and How to Find Freelance SQL Jobs

If Covid-19 has you all “I-want-to-stop-working-for-the-man-and-enjoy-a-more-fulfilling-life-as-the-master-of-my-own-destiny”, then I’ve got news for you. Not only is it possible to be an SQL freelancer, it’s also a potentially lucrative and liberating career move. It will allow you to work for a diverse range of clients and march to the beat of your own drum. Of course, SQL freelancing isn’t for everyone. You will need a strong sense of self-motivation, some serious hustling skills, and the ability to sell yourself and your services as THE ABSOLUTE BEST all the time, every time - day in, day out.

How to Convince Your Boss That You Need to Start Learning SQL

Learning SQL is a great goal. Now, if you could only convince your boss that it’s good for the company as well as for you ... You’re aware of the benefits of adding SQL to your skill set. You believe that the rewards gained from you learning SQL will also benefit your employer – it’s not just another way for you to develop your professional profile. But how do you articulate this to your boss?

Which Major Companies Use PostgreSQL? What Do They Use It for?

Which companies use the open-source relational database management system PostgreSQL? Find out … and learn why you should be a PostgreSQL user too. You know the blue elephant logo. You have heard that PostgreSQL is a very good solution. But which companies use it? Here is a list of the largest IT and business companies that use PostgreSQL (or Postgres, for short). Multinationals worth billions of dollars can't be wrong, right?

Advanced SQL Interview Questions (and Answers)

Do you want to move to a job that uses SQL? Are you unsure about what to expect during the job interview or how to benchmark your knowledge? This article will give you a good idea of where you stand. If you feel stuck in your job, you’re not the only one. The modern division of work pushes people to perform very specific tasks, expecting them not to look at what's on the other side.

What SQL Practice Do You Need to Prepare for a Technical Job Interview?

You’ve scored yourself an interview for an SQL-related job. Nice work! But perhaps uncertainty is creeping in as your interview date looms closer. Do you know enough SQL to make the cut? What questions are you likely to be asked? What SQL practice should you be doing before your interview? Almost all SQL job candidates go through exactly the same nerve-wracking process. Here at LearnSQL.com, we have the lowdown on all the SQL practice and preparation you’ll need to ace those interview questions and take your career to the next level.

Are There Any Good SQL Courses for Marketers?

Looking for places to learn SQL online and level up your marketing efforts? Check out these SQL courses. Introduction With the help of IT experts, meticulous marketers analyze information to create advertising strategies. This commonplace state of affairs forces the marketer to rely on data experts and sometimes wait for their availability. But what if marketers could pull the data themselves? They can – by turning into a technical marketer.

Types of Database Jobs: Choose One of Them and Start Being Awesome

Do you dream of high earnings and interesting work? Are you fed up with your boss and his or her annoying vacation stories in exotic countries? Is it time to change your job? Why not learn SQL? Here are some examples of the types of database jobs that may lead you to a better life. What types of database jobs use SQL? Here are some examples, but first, a small caveat.

How Will Learning SQL Improve My Daily Work?

Whether you want to boost your professional development, learn in-demand skills, or start something new and interesting, learning SQL will make your life easier in many ways. Are you thinking of learning SQL but aren’t sure if it's a good idea? At first glance, learning SQL may seem completely useless, especially if the industry you are in is not related to IT. But that's not true. Although your position in the company may not imply that you code every day, you can still gain a lot from SQL.

Should I Learn SQL as a Data Analyst?

So, you are a data analyst—someone who relies on data. You like to gather, clean, and transform data and come to conclusions based on data. You are a data detective. Which tool do you choose to do your job in an elegant, reproducible, and simple way? Excel? R? Python? Or should you learn SQL? Stay tuned! In this article, I will explain why SQL is a must-have skill for data analysts.

Top 10 Websites That Will Help You Find the Perfect SQL Job

People learn SQL for many reasons. In my case, I wanted to find a better job that would allow me to earn more and have more free time to pursue my interests. But where do you find such a job? Here is my list of the 10 best websites with database jobs. Although SQL is almost 40 years old, it is appearing in more and more job advertisements. Data has become an essential tool for entrepreneurs, and they are looking for people to squeeze every bit of information from their databases.

Common Entry Level SQL Developer Interview Questions

Have you ever been interviewed for an entry-level SQL position? Are you planning to apply for such a job? This article will help you to know what to expect and prepare for common SQL developer interview questions. After gaining some basic knowledge of SQL and programming, you're probably wondering what to do next. Or maybe you're not wondering! You know that what you've learned will soon disappear if you don't use it regularly.

How to Become an SQL Developer

There is no simple answer to the question “How do you become an SQL developer?” However, if the answer were too complex, there would be no point in writing this article, and yet I’m doing it. So, somewhere along the way, we’ll find the answer. As said in the intro, there is no magic wand that will turn you into an SQL developer. But reading this article will save you some time and help you focus on what is important to achieve your goal.

Why Use SQL Over Excel

SQL is replacing Excel in many fields, and data analysis is certainly one of them. If you are still using Excel as a data analyst, you are missing something very valuable. SQL can make your life easier, as it's more efficient and faster than Excel. So, how and from where can you learn SQL? How Can SQL Help Data Analyst? You can use SQL to help you with the following work:

Career Change: From Accountant to Database Designer

How do career changes and life choices impact our future? Can we change the path that's been set for us? And if so, where do we begin? I wouldn't blame you if you thought this article is about change. In a sense, it is—it's in the title, after all. But for me, this article is more about what remains constant. If somebody were to ask me what hasn't changed for me since my childhood, I would know the answer immediately: curiosity.

Complete SQL Practice for Interviews

Congratulations! Your SQL skills were strong enough to get you that job interview! Now, if you only knew what SQL questions and practical exercises a recruiter might ask you to do… This article is meant as a SQL practice for interviews. I’ll help you prepare for the SQL and database aspects of your job interview. In a previous article, I explained how can you boost your career by learning SQL.

Finding the Perfect SQL Job

So you have some SQL skills and you're looking for a job that will use them. What are your options? SQL is everywhere, and there's a huge demand for people with database management skills. This is especially the case when companies start implementing Big Data solutions and strategies. There's no arguing that SQL is a must-have skill. If you're already proficient, how can you put your expertise to practical use in the job market?

A Day in the Life of a SQL Developer

What is a SQL developer? And what does a SQL developer do? Describing a “typical” day for a SQL developer is not easy. When your daily work is using various technologies to create interesting database-oriented products, very few days are alike! Each day brings a new and intriguing challenge. Nevertheless, I’ll have a go at explaining what everyday things a SQL developer might do. Morning: Arrive at Work What does a SQL developer do after arriving at the office?

Tag: Join

SQL JOIN Topics That Require Practice

Are you interested in learning how to join tables in SQL? Where do you start? Many JOIN topics require practice. In this article, we’ll explore these topics by writing codes to solve real-life situations. Hopefully, you will learn which JOIN topics require attention. To make it easier for you, the topics are divided into beginner, intermediate, and advanced. Joining two or more tables in SQL lifts data analysis to another level.

How to JOIN Tables in SQL

Do you need to display data stored in different tables? Then it’s time to use SQL JOINs! This can be a challenging topic for beginners, so I’ve prepared this comprehensive step-by-step guide on joining tables in SQL. Often, the information that you want to display is stored in several tables. In such cases, you’ll need to join these tables by specifying which rows should be combined with other rows. That’s exactly what JOIN does.

SQL JOIN Tips for Beginners

If you’re a beginner and want to know how to start using SQL JOINs in your queries, you’ve come to the right place. Using the SQL JOIN clause is necessary if you want to query multiple tables. Sooner or later, you’ll have to use more than one table in a query. It’s the nature of relational databases in general – they consist of data that’s usually saved in multiple tables; in turn, these form a database.

What Is an SQL INNER JOIN?

How do you combine data from different tables in one query? An SQL feature called JOIN is the most common operator used to create complex queries. Learn the basics in this article. SQL allows us to select data from more than one table. In fact, the whole idea of using relational databases is selecting data from related tables. And we can use SQL’s JOIN operator to do this. There are many types of JOINs in SQL.

SQL Black Week 2020. See how much you can save!

Wow, have you seen what discounts the LearnSQL.com Team has prepared for Black Week? We’ve cut all the prices of our SQL courses. We also have something special for students. But hurry up, time is short! Black Week - Special Pricing: Individual SQL course - $25 Forever plan - $179 Forever plan for Students - $90 We know just how much you love to bag great discounts. SQL Black Week 2020 is on!

SQL JOIN Types Explained

What’s the difference between INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN in SQL? When should you use each one? We’ve got your answers right here. You want to combine data from two or more different tables, but you’re not sure how to do it in SQL. No worries. In this article, I will show you how to use the SQL JOIN clause to merge data from two tables.

How to Join Two Tables in SQL

Querying data from multiple tables is very common when working with relational databases. It is not difficult if you know how to use the dedicated SQL operators for doing this. In this article, you will learn how to join two tables by using WHERE and by using a special operator JOIN, and you will see how to filter rows in the result set. If you want to practice joining tables in SQL, check out our interactive SQL JOINs course.

How to Practice SQL JOINs

There is no better way to learn SQL joins than through practice. However, there will probably be obstacles along the way. I’ll cover some of these obstacles and give ideas for how to overcome them. While this article won’t turn you into SQL JOINs expert, it will show you how to become one. So, let’s start! Challenges When Practicing SQL JOINs It’s hard to answer “How do you master SQL JOINs?

Converting Subqueries to Joins

Not all queries are alike, especially in terms of performance. In this article, we'll look at how you can convert SQL subqueries to joins for improved efficiency. When should I use SQL subqueries? Great question! Unfortunately, there's no concrete answer. SQL beginners tend to overuse subqueries. Typically, once they find that SQL construction works in one situation, they try to apply that same approach to other situations. It's only natural.

SQL Hacks To Control Family Budget On Black Friday Weekend

If you’re in the US, chances are you’ve been eagerly awaiting the approach of Black Friday just as much as Thanksgiving. Though the shopping frenzy takes hold of nearly everyone, some people have to stick to their budgets and shop prudently. In this article, we’ll take a look at how generating an SQL report can help you track how much your family spent shopping on Black Friday. Storing Black Friday Purchases in a Database Before we can create an SQL report, we first need some data we can use.

An Illustrated Guide to Multiple Join

So far, our articles in the "An Illustrated Guide" series have explained several join types: INNER JOINs, OUTER JOINs (LEFT JOIN, RIGHT JOIN, FULL JOIN), CROSS JOIN, self-join and non-equi join. In this final article of the series, we show you how to create SQL queries that match data from multiple tables using one or more join types. Join Types in SQL Queries Before we start discussing example SQL queries that use multiple join types, let's do a short recap of the join types we've covered so far, just to be sure you understand the differences.

An Illustrated Guide to the SQL Non Equi Join

Did you know that in SQL, a join doesn’t have to be based on identical matches? In this post, we look at the SQL non equi join, which uses ‘non-equal’ operators to match records. We’ve already discussed several types of joins, including self joins and CROSS JOIN, INNER JOIN and OUTER JOIN. These types of joins typically appear with the equals sign (=). However, some joins use conditions other than the equals (=) sign.

An Illustrated Guide to the SQL Self Join

What is an SQL self join and how does it work? When should it be used? We’ll provide answers to those questions! In SQL, we can combine data from multiple tables by using a JOIN operator. JOIN has several variants; we’ve already discussed CROSS JOIN, INNER JOIN, and OUTER JOIN. Most of the time, these operators join data from two or more different tables. You can practice all the different types of JOINs in our interactive SQL JOINs course.

How to Track Down Duplicate Values in a Table

When it comes to information management, duplicates present one of the most common challenges to data quality. In this article, I'll explain how it is possible to find and distinguish duplicate names with the help of the SQL data programming language. I really like my maiden name. The reason I like it so much is because it's rare. My maiden name (first with last) provided a unique identifier on platforms such as LinkedIn, Facebook, Twitter and similar.

An Illustrated Guide to the SQL OUTER JOIN

We’ve already discussed the SQL CROSS JOIN and INNER JOIN statements. It’s time to explore another: OUTER JOIN. What is it? How does it work? Let’s find out! If you’ve read our other posts, you know that you can link the data in two or more database tables using one of the many types of SQL join operator. Today, we’ll discuss the three kinds of OUTER JOIN: LEFT OUTER JOIN, RIGHT OUTER JOIN, and FULL OUTER JOIN.

An Illustrated Guide to the SQL INNER JOIN

What is an SQL INNER JOIN, and how does it work? Let's find out! In my last article, I discussed the CROSS JOIN operation in SQL. Today, we'll look at INNER JOIN and how to use it. Is it the same as a JOIN? How many tables can you link with an INNER JOIN? These are all good questions. Let's look at the answers! What is an INNER JOIN?

An Illustrated Guide to the SQL CROSS JOIN

What is an SQL CROSS JOIN statement? When should you use it? When shouldn't you use it? This post will tell you what you need to know about CROSS JOIN. You already know that you can use the SQL JOIN statement to join one or more tables that share a matching record. And if you're read the LearnSQL's post Learning SQL JOINs Using Real Life Situations, you know that there are many types of JOINs.

An Introduction to Using SQL Aggregate Functions with JOINs

Previously, we've discussed the use of SQL aggregate functions with the GROUP BY statement. Regular readers of the our blog will also remember our recent tutorial about JOINs. If you're a bit rusty on either subject, I encourage you to review them before continuing this article. That's because we will dig further into aggregate functions by pairing them with JOINs. This duo unleashes the full possibilities of SQL aggregate functions and allows us to perform computations on multiple tables in a single query.

Learning JOINs With Real World SQL Examples

The JOIN statement lets you work with data stored in multiple tables. In this article, I’ll walk you through the topic of JOIN clauses using real world SQL examples. Imagine if you could only work with one database table at a time. Fortunately, this isn’t anything we have to worry about. Once you learn the JOIN statement, you can start linking data together. In this article, I’ll use real world SQL examples that illustrate how we use JOINs, how each type of JOIN works, and when to use each type.

SQL JOINs

A SQL JOIN is a method to retrieve data from two or more database tables. This article presents a basic overview of what data from a particular SQL join will look like. A popular way of understanding SQL joins is to visualize them using Venn diagrams, so each example have corresponding Venn diagram, appropriate SELECT statement and the result table. There are a few major kinds of SQL joins:

SQL JOINs for Beginners

You’re probably already familiar with simple SQL queries, such as SELECT * FROM table. Now you are wondering what to do when you have multiple tables, and you want to join them. Exactly! JOIN is the key. In this SQL JOINs tutorial for beginners, you will learn how to connect data from multiple tables. What are SQL JOINs? Databases usually have more than one table. JOINs are an SQL construction used to join data from two or more tables.

Tag: Joins

What Is the OUTER JOIN in SQL?

Even if you are new to SQL, you must have come across the term OUTER JOIN. In this article, I will explain what OUTER JOIN in SQL does. I’ll use some practical examples to demonstrate how it is used in day-to-day SQL applications. If you want to use SQL for practical purposes, learning the different JOINs is extremely important. In fact, you will be using a JOIN in just about every second query you write.

5 Best Practices for Writing SQL JOINs

These best practices for SQL JOINs will help you make readable SQL queries that deliver accurate, clear, and understandable output. Considering that relational databases are built around related tables, it’s no wonder that SQL JOINs – which allow you to combine information from multiple tables – are one of the primary skills acquired by SQL newbies. SQL JOINs course by LearnSQL.com is the perfect place to refresh your knowledge about JOINs.

How to Join Only the First Row in SQL

In your projects, you may encounter situations when you have many orders corresponding to one customer or many temperature observations corresponding to the same location, but you only need to join the first row with the most recent order or the most recently observed temperature to the corresponding record in another table. In this article, I’ll go through several ways to do this in SQL. The Problem There are many different scenarios where you have a one-to-many relationship between two tables and you need to join only the first match from one table to the corresponding record in another.

Best Places to Practice SQL JOINs Online

You’ve just started your journey with SQL and you’re not sure what a JOIN is or where to use it. Don’t worry! In this article, you will find out what JOINs are and where you can practice them online. If you have just started learning SQL, you have a lot of topics to cover before you can call yourself a data professional. If you are serious about using SQL, you’ll have to understand JOIN – what it does, when you can use it, and what its different variants do.

7 SQL JOIN Examples With Detailed Explanations

Do you need to join several tables to get the necessary result set? The SQL JOIN is a basic yet important tool used by data analysts working with relational databases. And I understand it can be difficult to choose from the zillions of introductory guides to joins. In this article, I will focus on real-world examples with detailed explanations. Introduction to JOIN With relational databases, the information you want is often stored in several tables.

Where to Practice JOINs in MS SQL Server

Are you tired of looking for exercises that will help you master SQL JOINs in MS SQL Server? Find out about an online course that will take your JOINs skills to the next level! There are tons of MS SQL Server courses out there. Some are good, although they often lack the most important thing ... the possibility of practicing what you learn with interactive exercises. This is one of the main reasons I advise people (especially beginners) not to learn SQL exclusively from YouTube clips.

What Is a Self Join in SQL? An Explanation With Seven Examples

The self join is a popular special case of the SQL JOIN. While most JOINs link two or more tables with each other to present their data together, a self join links a table to itself. This is usually done by joining a table to itself just once within a SQL query, but it is possible to do so multiple times within the same query. Typically, each table in a database stores a specific type of information.

How to Join the Same Table Twice

JOIN is one of the most common statements in SQL. As you may know, it is used to join and combine data from two or more tables into one common data set. In this article, I’m going to discuss special types of joins? in which you combine the same table twice—including joining a table to itself, also known as the self join. When and why do you need to do this?

SQL JOIN Cheat Sheet

Download this 2-page SQL JOIN Cheat Sheet in PDF or PNG format, print it out, and stick to your desk. The SQL JOIN Cheat Sheet provides you with the syntax of different JOINs, and examples. You can download this cheat sheet as follows: Download 2-page SQL JOIN Cheat Sheet in PDF format (A4) Download 2-page SQL JOIN Cheat Sheet in PDF format (Letter) Download 1-page SQL JOIN Cheat Sheet in PDF format (A3) Download 1-page SQL JOIN Cheat Sheet in PDF format (Ledger) SQL JOINs Cheat Sheet JOINING TABLES JOIN combines data from two tables.

Can you Join two Tables Without a Common Column?

Yes, you can! The longer answer is yes, there are a few ways to combine two tables without a common column, including CROSS JOIN (Cartesian product) and UNION. The latter is technically not a join but can be handy for merging tables in SQL. In this article, I’ll guide you through the different solutions with examples. When Do you Need to Join Tables Without a Common Column? Beginners just getting started with SQL are usually introduced to standard equi joins, in which two tables are combined by a common column.

What's the Difference Between Having Multiple Tables in FROM and Using JOIN?

What’s your approach to joining tables in SQL? In this article, we discuss two approaches and explain why many SQL developers have a definite preference for JOIN. Do you prefer to list multiple tables in FROM and use WHERE to set the join conditions? Or do you use the JOIN keyword? SQL supports both, but there are significant differences between them. Let’s look at each one in detail and then discuss why JOIN is generally preferred.

Practical Examples of When to Use Non-Equi JOINs in SQL

If you think that two tables in SQL can be joined only using the common field, you will be excited to learn that there are other ways of joining. Non-equi JOINs use different kinds of comparison operators in the JOIN condition. In this article, I’ll guide you through non-equi JOIN examples to show the common use cases for this type of JOIN. Equi JOIN vs. Non-Equi JOIN How do you usually join two tables in SQL?

How to Learn SQL JOINs

JOINs are one of the most fundamental and commonly used SQL commands for manipulating and querying real-world data sets. They are also one of the more challenging SQL topics to master! In this article, you’ll learn an effective strategy to learn the different types of SQL JOINs. When data is stored in a single table, we can easily retrieve rows and get all the information we need. But when businesses scale, so does their data.

Subquery vs. JOIN

One of the challenges in writing SQL queries is choosing whether to use a subquery or a JOIN. There are many situations in which a JOIN is the better solution, and there are others where a subquery is better. Let’s consider this topic in detail. Subqueries are used in complex SQL queries. Usually, there is a main outer query and one or more subqueries nested within the outer query.

How to Join 3 Tables (or More) in SQL

Using JOIN in SQL doesn’t mean you can only join two tables. You can join 3, 4, or even more! The possibilities are limitless. If you’ve just learnt JOINs in SQL, you might think that it’s limited to two tables. That’s not surprising – this concept can be hard to understand, and the idea that JOINs can get even more complicated may be really scary at first. The truth is that you can easily extend this idea to three tables or even more.

How to LEFT JOIN Multiple Tables in SQL

Can you LEFT JOIN three tables in SQL? Yes, indeed! You can use multiple LEFT JOINs in one query if needed for your analysis. In this article, I will go through some examples to demonstrate how to LEFT JOIN multiple tables in SQL and how to avoid some common pitfalls when doing so. What Is a LEFT JOIN? Let’s start by reminding ourselves what a LEFT JOIN is and how to use it.

Tag: Keys

Why Do Relational Databases Use Primary Keys and Foreign Keys?

Relational databases organize data in a standardized manner. All data is entered into tables, the so-called relations. The tables are linked with one another to create connections between the data. The backbone of any relational database is the primary and foreign keys. Read along to find out why they are so important. In this article, we focus on the reasons why relational databases use primary and foreign keys. First, we review what primary and foreign keys are.

Tag: Kurtosis

High Performance Statistical Queries –Skewness and Kurtosis

In descriptive statistics, the first four population moments include center, spread, skewness, and kurtosis or peakedness of a distribution. In this article, I am explaining the third and fourth population moments, the skewness and the kurtosis, and how to calculate them. Mean uses the values on the first degree in the calculation; therefore, it is the first population moment. Standard deviation uses the squared values and is therefore the second population moment.

Tag: Language

What Programming Language Should You Learn?

If you've ever been wondering which programming language you should learn first, you know that's a tough nut to crack. It’s especially difficult if you are new to IT and programming. In this article, I give suggestions for what to learn first and what perspectives each language can give you in IT. There are hundreds of programming languages, and new ones are showing up all the time. Getting to know all of them is simply impractical and impossible.

Tag: Learn sql

Free Course of the Month – SQL Practice Set in PostgreSQL

Do you know the basics of PostgreSQL but still need some practice? Look no further! Here is a great interactive course, SQL Practice Set in PostgreSQL. Throughout the month of September, you have access to it for FREE! We at LearnSQL.com believe that to learn a new skill, you need basic theoretical knowledge and, above all, a lot of practice. It's the same with writing PostgreSQL queries – you need a lot of PostgreSQL practice.

How to Learn SQL for Marketing Analytics With LearnSQL.com

SQL is a valuable tool for any experts wanting to make data-driven decisions. Marketers are no exception. Let's explore how to design an effective learning path for SQL in marketing. SQL for marketing analytics is used to understand customers better and to increase the effectiveness of marketing campaigns. If you work in marketing and want to join other marketing experts who have already benefited from this tool, you need to learn SQL.

What's New in MS SQL Server 2022

Microsoft SQL Server 2022 is almost here! In this article, we’ll review what new enhancements and features will be coming to this popular relational database. The new version of MS SQL Server will become available almost three years after SQL Server 2019 was released. (You can learn more about the origins and different versions of SQL Server in A Brief History of MS SQL Server.) If you need to start implementing a software solution, there are plenty of changes and new features in SQL Server 2022 that makes it a great option.

How to Learn SQL

It takes quite an effort to learn SQL or any new skill for that matter. But pushing hard is not enough to learn it successfully. You can sit for hours and still feel like you're not making progress. So, what do you do? Let it go or try even harder? I say: work smart, not hard. SQL (Structured Query Language) is one of the most popular programming languages. It is an invaluable tool in a world overflowing with data.

LearnSQL Track of the Season: Creating Database Structure

Summer is a great time to learn something new! Have you heard about data engineering? It’s one of today’s hottest skills. In this article, I'll show you why we selected our Creating Database Structures track as our SQL Track of the Season – and why it’s your ticket to a new career! LearnSQL.com offers online SQL training tracks – logically structured and well-thought-out learning paths that will help you work towards becoming an SQL expert.

PostgreSQL vs. MySQL: Is It Difficult to Switch?

So you know PostgreSQL, but the boss has decided to switch to MySQL. What are the differences between these two SQL dialects? We discuss PostgreSQL vs. MySQL in this article. PostgreSQL has gained popularity in the last decade, and many developers and database specialists learned PostgreSQL as their first SQL dialect. But PostgreSQL is not the only relational database; during your IT career, you will probably be asked to use another SQL dialect – like MySQL.

What Is an SQL Query?

An SQL query is the most basic SQL command. It is a question you ask a database. In this article, we dive into the basics of SQL queries to kickstart your SQL journey with practical knowledge right away! SQL, or Structured Query Language, is a programming language designed to interact with databases. When you want to access data in a database, be it to alter, delete, add, or simply extract information, you use SQL.

Lesser-Known SQL YouTube Channels You Need to Follow Now!

Are you learning SQL? Many beginners start with YouTube tutorials. However, popular SQL clips are not always very helpful. You need to know which ones to watch so that you don't waste your time. In this article, I discuss SQL YouTube channels that, while not the most popular, deserve your attention. Click "subscribe" and watch! Those who follow my articles on LearnSQL.com know I'm not a huge fan of learning SQL from YouTube.

How to Set Up a Company SQL Training Program with LearnSQL.com

Are you looking to set up a business or corporate SQL training for your company's employees? In this article, we’ll discuss how to build an efficient SQL training program and why the LearnSQL.com platform is the choice of leading tech companies. If you are responsible for employees’ professional development – especially in a data-driven company – you know that SQL is essential for anyone who works with data. This programming language can enhance the performance of data and business analysts (for whom SQL is often a primary tool) as well as marketers, salespeople, HR specialists, auditors, and many more.

How to Get More from Your BI Tools with SQL

Are you frustrated with the limitations of your business analytics tool? Do you wonder if there are other features you could tap into? Would you like to know how SQL compliments your work with Power BI and Tableau? Read this article to learn more! If you are a data analyst or if data analysis is part of your everyday job, Business Intelligence (BI) tools are crucial for your work. You also know that most databases run SQL queries in the background of such tools.

I Already Know PostgreSQL. Is it Hard to Start Using MS SQL Server?

What are the differences in PostgreSQL vs. MS SQL Server? We discuss the similarities and the differences between these two popular SQL dialects. Many of us developers and database specialists began working with free relational databases like PostgreSQL or MySQL for personal projects or small organizations. Some of us have since moved on to organizations using MS SQL Server and have had to learn to use the new tool. You may be wondering how challenging that is and whether you would struggle with SQL Server under similar circumstances.

What Is SQL Used For?

So you’ve heard about databases and SQL, but you’re not sure what the big deal is. Read on to find out why data skills like SQL are so important. It seems like every other job requires you to know something about data, databases, and SQL. But what are these things, and what are they used for? Who even uses SQL? That’s what we’ll discuss in this article. Why Data Is So Important The Internet and the technology revolution have brought unprecedented opportunities.

An Overview of SQL Text Functions in MySQL

Do you work in MySQL as a data analyst? Then you should know how to use its text functions – data analysts don’t work only with numbers. Reporting requires computations, data classification, and label creation, and you can do all of that in MySQL.  In this article, I’ll explain several of the most common and useful MySQL text functions by discussing what they do and showing how they do it.

What Is SQL?

SQL may be something you hear about from your colleagues. Or you may see it in the job description for your dream role or notice it in a list of the most popular programming languages. So, what is SQL? Should you learn it? Let's find out. Do you think about a career in data analysis and data science? Do you need to interact with relational databases at work? Do you want to improve your performance as a marketer, HR specialist, or researcher by making more informed decisions?

An Overview of Microsoft SQL Server Text Functions

Data analysts use text values when creating SQL reports. You can create your own labels with functions, classify rows based on text value, or do computations based on it. This article covers how to do all that. The text values in databases are not just for reading. As with numeric values, we perform operations on them and manipulate the text. SQL Server has a fair number of text functions.

Learn SQL in 4 Steps

Want to work with data? You’ll need SQL. Fortunately, you can learn SQL in just 4 steps! If you are interested in data crunching or working with data in general, you’ve probably heard something about SQL. Now that data storage is cheap and accessible, data from every transaction can be stored and analyzed. Hence, there’s great demand for people who can capture and work with this data. We’ve even seen entire companies profit from being proficient with data; for example, consider the ever-growing value of Google and Facebook (now Meta).

These SQL Queries Will Help You With Data Analysis

Need to streamline your everyday data analysis tasks? This article explains how basic SQL queries can help. If you are planning a corporate career or any field that involves working with data, you must have come across SQL, or Structured Query Language. SQL was first developed in the 1970s and it continues to be the industry standard for database interactions. Many of you may already have decided to learn this language, given how powerful it is.

How to Combine Two Aggregate Functions in SQL

Having trouble using two aggregate functions in one query? This article will show you how to do it the right way – actually, the two right ways. In data analysis and reporting, we often need to count the number of records or sum them up and then calculate the average of this count or sum. Translated to SQL logic, this is the aggregation of aggregated data, or multi-level aggregation. For aggregation purposes, there are the SQL aggregate functions.

How to Install a MySQL Database on a Windows PC

Do you want to install a MySQL database on your Windows computer? And maybe find out how to start using a MySQL database? In this article, we’ll cover the installation process. MySQL is one of the most popular relational database servers. This is one reason to start using a MySQL database. Among the various editions of MySQL delivered by Oracle, the Community edition is available for free. You can download it from the MySQL website.

Over 40 and Want to Upskill? Learn SQL!

You have several years of experience. Your work has even been written up in a few case studies. Yet, you still have a hard time finding the right path to improve your career. If that's true for you, the answer is to learn SQL. In this article, I'll tell you why. Why learn SQL when you’re already an experienced professional? It’s always good to learn something new. You may want to pick up a new hobby, try out a different industry, or get a new skill to help your career.

How to Use the COALESCE() Function in SQL

SQL users are often faced with NULL values in their queries and need to process them properly. The COALESCE() function helps handle NULL values. Read this article to learn how to use COALESCE() in your queries. SQL tables store data in records, and records are composed of fields. There can be situations where we don’t know the value for a specific field. For example, let’s suppose we have a table with data for persons.

The Recent Rise of DBT and the Analytics Engineer

If you’re interested in data engineering or data analytics, you should know about DBT. And you should also learn about the role of an analytics engineer. We cover both in this article. The rise of Cloud data providers has led to new challenges and possibilities. If you are thinking about entering the data analytics space, it is important to be aware of them; it can help you decide what roles to aim for and what skills to learn.

Top 9 SQL GROUP BY Interview Questions

Preparing for an SQL job interview? This guide will walk you through nine basic, intermediate, and advanced GROUP BY questions that you may have to answer. There are common GROUP BY questions that pop up in a lot of SQL job interviews; in this article, we’ll explain how to answer them. If you are a data analyst or another data professional preparing for an interview, this article aims to help you out.

What Are Window Functions in SQL?

In this article, we discuss what window functions are and how they help you do your job as a data analyst or specialist. No, window functions have nothing to do with the operating system. The window here refers to a set of rows over which the function aggregates data. To learn how window functions work, what functions there are, and how to apply them to real-world problems, it’s best to take the Window Functions course.

Why Should Every Data Analyst Know SQL?

In the 1980s and 90s, it was the emergence of ERPs, processing a few thousand transactions a day. Now, sophisticated Cloud-based systems work with billions of transactions each day. How data is captured and handled has come a long way! Anybody who understands how to use this data has an edge. The good thing is that while the technology working in the background has become more complex, we don’t necessarily need to understand the underlying system’s details to use it.

Free SQL Course of the Month – PostgreSQL INSERT, UPDATE, and DELETE Commands

Do you want to be a data engineer or data analyst? Do you work with databases daily and need to expand your skill with the basics of data manipulation? You've come to the right place. For May 2022, our SQL course of the month is PostgreSQL INSERT, UPDATE, and DELETE Commands! Learn SQL for FREE! How do you get this free PostgreSQL course in May? Create a free LearnSQL.

How to Update Only the First 10 Rows in SQL

Real-world databases require continuous updating. Often, you need to update specific records; you may even want to update only the first row, or the first 10, 100, or 1000 rows. Let’s explore how to update rows for a specified quantity from the top in SQL. What Is the SQL UPDATE? In SQL, an UPDATE statement modifies existing records of a table. You may choose to update entire columns or update rows filtered with a WHERE statement.

Top 5 MySQL Query Tools

Are you looking for a software solution that will make working with the MySQL database even easier? In this article, I’ll tell you about five highly recommended query tools that will save you time. MySQL may already be familiar to you as the most popular open-source relational database management system (DBMS). It works in most applications, which is why the last Stack Overflow report rated MySQL as the most used database.

The SQL Syntax Is Simple: True or False?

Are you contemplating learning SQL but are concerned about how difficult it may be, especially if you have no prior coding experience? If so, you are not alone. In this article, I show you how simple SQL is and that it is worth your time learning it. You just need to know how to approach it properly. Many people carry the notion that learning SQL is much like learning other programming languages.

What Are the Different SQL JOIN Types?

You just can’t understate the importance of the JOIN when learning SQL. Not only is it one of the most fundamental operations in relational databases, but it is also very versatile with many different types. Although SQL JOIN may be intimidating at first, it becomes a very handy instrument in your arsenal once you understand it. Let’s explore all the SQL JOIN types! We can safely say the JOIN operation is one of the most powerful features of SQL.

SQL Track of the Season: SQL from A to Z in MySQL

Do you feel the spring already? Everything is in full bloom at this time of the year. Why shouldn’t it be the same with your career? You just need to water it with a new skill. Here is the brilliant SQL from A to Z in MySQL track, our Track of the Season. In this article, I answer common questions about this awesome set of online MySQL courses. Why should you care about relational databases at all?

Join the LearnSQL.com Affiliate Program!

Are you a creator, blogger, or YouTuber? Do you have an audience, do you appreciate our interactive SQL courses, and would you like to help promote them? By the way, you can earn some money! Here is our SQL Affiliate Program. We create our SQL courses with a passion and a love for databases. Looking at the reactions and the reviews of our users, we do quite well. If this is your first visit to LearnSQL.

Are You a Student? Choose LearnSQL.com

If the answer to this question is yes, then let’s talk about how learning SQL as part of your educational journey benefits you down the road. We’ll focus on the importance of SQL for students – whether you are preparing for an exam, are thinking about a career in IT, or need new skills for a research project. Later, we will explain why LearnSQL.com is the way to go, whatever your learning goals are.

How to Write Multiple CTEs in SQL

Leverage the full potential of the CTE by combining two or more of them in a single SQL query. Common table expressions, or CTEs, can be a powerful SQL tool. When you write two (or even more) CTEs together, this power multiplies. In this article, I’ll show you three ways of writing multiple CTEs: Using two independent CTEs in one SQL query. Using two CTEs where the second CTE refers to the first.

The SQL Substring Function in 5 Examples

Working with text data in SQL? We explain how to get values from any point in a string. When you think of working with data in SQL, your first thought is probably a database full of numbers and your SQL code doing very fancy calculations. But text is data, too! It’s very common to find text data in databases. Not only do you have to extract it, but often you also have to manipulate it.

Are You Ready to Become a Data Analyst?

Data analysts enjoy strong career prospects. Do you have the skills required for this role? Let’s find out! If you enjoy working with data, searching for interesting patterns and valuable insights, you may wonder “Should I become a data analyst?” In this article, I’ll explain what data analysts do and what skills a successful data analyst needs. What Does a Data Analyst Do? Data-driven organizations rely on specialists who know how to get value out of data.

SQL and Cloud Databases Are the Perfect Match!

Do you want to do analytics in the cloud? Are you considering learning SQL and wondering whether you can use it with cloud-based databases? Do you want to know how cloud databases and SQL work together? We answer your questions in this article. Read on! You may be an analyst who has heard about cloud databases and SQL and want to learn more. Maybe you are already familiar with them and want to know if the two technologies fit together.

Is Your Learning SQL Plan Stuck in Neutral?

Are you stuck on some tricky point of learning SQL and don't know how to move on? This article will help you move on in your SQL journey. Have you been learning SQL, only to get discouraged by some difficult concept? Everybody gets stuck when they try to learn something new. Most of us have probably given up trying to learn that thing, only to come back to it later.

New MySQL Courses Are Here!

A lot of you have been waiting for new MySQL courses on LearnSQL.com – and finally, they’re here! Now you can learn everything MySQL in a simple, understandable, and fun way. We've worked a lot with these online SQL courses and created hundreds of interactive exercises to help you learn this popular SQL dialect. If you want to communicate with the world’s most popular open-source database, our MySQL courses will help you achieve that goal!

LearnSQL.com’s Monthly SQL Practice in 2022

Are you looking for ways to practice SQL? Tired of boring exercises based on unreal scenarios? We have something for you! Every month, we publish a new set of SQL practice exercises. You'll find all of them in the monthly SQL Practice. Here at LearnSQL.com, we believe the best way to learn SQL is through practice. All of our SQL courses (and there are over 30 of them!) are hands-on.

An Overview of MySQL Data Types

What data types are available in a MySQL database? In this article, you’ll learn about numeric data types, text data types, and much more! You may have seen our article about data types in SQL. Here, we focus on the MySQL data types. We will discuss the most commonly used ones: numeric, text, and date and time. If you are interested in the topic, be sure to check out our Data Types in SQL course.

2nd Anniversary of LearnSQL.com

It’s happening! Today we celebrate the 2nd anniversary of Learn SQL.com. We have come a long way together. Thank you for being with us and we promise to get even better every day! 731 days have passed since February 23, 2020, when we launched the LearnSQL.com platform. That's 17544 hours or 63158400 seconds if you prefer. It's been a long time, but it feels like yesterday that we started out together.

How to Query a Parent-Child Tree in SQL

What are parent-child tree structures in SQL? In this article, we answer that question, talk about query hierarchy, and demonstrate the five most common SQL queries you’ll need for these data structures. Yes, you can use SQL on a parent-child tree structure. I’ll show you how in this article. Along the way, I’ll walk you through five query examples, starting with the easiest and ending with the most complex.

Is Learning PostgreSQL in 2022 Worthwhile?

You want to take a SQL course, but selecting the right one can be too challenging. Perhaps you don't know which dialect you should start with? PostgreSQL is one of the best options. Check out if it is worth it to learn PostgreSQL in 2022. When you search the web, there are many job advertisements for database specialists. Perhaps that is why you have chosen the direction toward development. Or maybe you are just fed up with Excel in your day-to-day duties (which is not surprising) and want to make work easier.

How Do You Get Rid of Duplicates in an SQL JOIN?

Do you have unwanted duplicates from your SQL JOIN query? In this article, I’ll discuss the possible reasons for getting duplicates after joining tables in SQL and show how to fix a query depending on the reason behind the duplicates. Data analysts with little experience in SQL JOINs often encounter unwanted duplicates in the result set. It’s challenging for beginners to identify the reason behind these duplicates in JOINs.

The SQL OVER() Clause Explained

Here is a detailed explanation of the OVER() clause in SQL window functions. This is a detailed guide on using the OVER() clause in SQL window functions. I will focus specifically on this clause, which requires that you have at least a general idea of how window functions work. To make the best out of this article, take a look at the SQL Window Functions Cheat Sheet. Feel free to have it by your side as we go.

PostgreSQL Interview Questions and Answers

Job interviews are always stressful. Interviewing and getting asked technical questions about PostgreSQL is even more of a challenge! In this article, we’ll cover some of the PostgreSQL interview questions you can expect when applying for a new job. By the end of the article, you should be able to handle most of the questions you are likely to face. We’ve previously covered common questions you can expect at a SQL job interview, but this article will be focused on Postgres specifically.

What Is a Common Table Expression (CTE) in SQL?

The common table expression (CTE) is a powerful construct in SQL that helps simplify a query. CTEs work as virtual tables (with records and columns), created during the execution of a query, used by the query, and eliminated after query execution. CTEs often act as a bridge to transform the data in source tables to the format expected by the query. A common table expression, or CTE, is a temporary named result set created from a simple SELECT statement that can be used in a subsequent SELECT statement.

The Top 5 SQL Courses and Learning Platforms for 2022

It’s the New Year! Time to start thinking what good you can do yourself in 2022. If you haven’t decided yet, we want to recommend learning something new – specifically, learning SQL. Maybe learning SQL is already on your 2022 to-do list. If so, take it seriously – learning SQL can change your career path and even your life! It makes sense to find the best SQL courses so you can learn effectively.

Free Course of the Month – PostgreSQL JOINs

Our PostgreSQL JOINs course will help you consolidate your knowledge of working with data from two or more tables in a PostgreSQL database. Throughout the month of January, this awesome SQL course is absolutely FREE! Wondering why we want to give you this SQL course for free? We've been doing this for a long time. Every month, we choose one of our interactive online SQL courses and give users free access to it.

How to Include Zero in a COUNT() Aggregate

Explaining how to include zero (0) counts in your SQL query result. Here’s the problem: you want to count something that doesn’t exist, and you want to show your result as zero. How do you do that in SQL? Using the COUNT() aggregate function is a reasonable first step. It will count all the data it finds and return the number of occurrences. But what if there are no occurrences of certain data?

Is SQL Case-Sensitive?

Is SQL case-sensitive? The question seems simple, and you may think it’s a yes-no question. However, the answer depends on multiple factors. Let’s take a look at the possible answers. First of all, this question can be understood in multiple ways. Which part of SQL are you asking about? Do you mean keywords (e.g., SELECT, WHERE, etc.), table and column names, or values in the columns? Which database management system (DBMS) do you have in mind?

Christmas SQL Scholarship 2021

We know 2021 was very difficult for many of you. Now that it is slowly coming to an end, we’ve decided to end it with something positive. Here is the Christmas SQL Scholarship 2021! Let's enter the new year together with new energy and a chance for change! It was another year in which Coronavirus did not give up. The crisis has also affected the economy and our wallets.

Top 5 MS SQL Server Courses for Beginners

Every journey, including a career change, begins with the first step. If you're thinking about learning data analysis or strengthening your MS SQL Server skills arsenal, you've come to the right place. Here are the top 5 MS SQL Server online courses. Enjoy! You've probably heard that today’s organizations rely heavily on data analysis. You heard right. They are looking for employees who can navigate the world of databases and draw conclusions from data.

Will SQL Ever Be Replaced?

Is it worth learning SQL? Is it possible that one of the modern programming languages or no-code solutions will replace SQL very soon? No; it is not that easy to replace SQL and relational databases. Let’s see why SQL is future proof – and why learning it will pay off for many years to come. If you are building your career in a data-driven company, you are probably looking into opportunities to enhance your skill set in data management and data analysis.

Free Course of the Month – Common Functions in PostgreSQL

Do you want to be able to use popular PostgreSQL functions and process different types of data more easily? You've come to the right place! Here is the Common Functions in PostgreSQL course. Throughout the month of December, this SQL course is absolutely FREE! You are probably wondering: why is LearnSQL.com offering a free SQL course? Well, we've been doing this for a long time. We choose one of our courses every month and give users free access to it.

5 SQL Subquery Examples

SQL subqueries are basic tools if you want to communicate effectively with relational databases. In this article, I provide five subquery examples demonstrating how to use scalar, multirow, and correlated subqueries in the WHERE, FROM/JOIN, and SELECT clauses. A subquery, or nested query, is a query placed within another SQL query. When requesting information from a database, you may find it necessary to include a subquery into the SELECT, FROM , JOIN, or WHERE clause.

Black Week 2021 is Here!

We know you've been waiting for it, and it's finally here: Black Week, and with it, a great promotion for our SQL courses. This is the best offer in the history of LearnSQL.com! Sometimes we surprise ourselves. Last year's Black Week promotion on theAll Forever Plan and individual courses was great, many people took advantage of it, and we thought it would be hard to come up with something better.

SQL for Startups – Do You Need It?

If you’ve been wondering whether to use SQL in your startup, it’s probably high time to do so. SQL can be an amazing tool for small, fast-growing businesses. But don’t worry if you’re unfamiliar with SQL for startups. Maybe you are not sure what SQL is all about. Don’t worry; you don’t have to make any decisions this second! First, answer these questions: Can you think of any data related to your business – prices, clients, details about clients, production details, budget, costs, strategy, or anything else?