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Articles
Cookbook
9 Apr 2021
Kateryna Koidan
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. Table of Contents Introduction to JOIN INNER JOIN Example #1: Showing books and their authors Example #2: Showing books and their translators LEFT JOIN Example #3: Showing all books alongside their authors and translators, if they exist Example #4: Showing all books with their editors, if any RIGHT JOIN Example #5: Books and editors with RIGHT JOIN FULL JOIN Example #6: Showing all books and all editors Example #7: Showing all books, authors, editors, and translators Time to Practice SQL JOINs!
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8 Apr 2021
Zahin Rahman
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.
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7 Apr 2021
Jakub Romanowski
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?
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6 Apr 2021
Tihomir Babic
How to Find the Next Non-NULL Value in SQL
You need to find the next non-NULL value in a time series, but you don’t know how. Can you even do that in SQL? Yes, you can! This article will show you what to do. If you work with SQL, you will sooner or later confront NULL values. Having NULLs in a database is almost unavoidable. However, sometimes you want to avoid them in your reports. This is quite often true when you’re analyzing time series data; NULL values mean there’s no data available.
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2 Apr 2021
Kateryna Koidan
What Is the RANK() Function in SQL, and How Do You Use It?
Who are your top 10 customers? Who are the top-performing employees in each department? To answer questions like these, you’ll need to rank the output of your SQL query. Let’s see how the RANK() function assists with ranking results in SQL. There are many use cases in which you might need to rank rows in SQL. You may want to rank customers based on the sales volume, students based on their exam results, company assets based on their present value, departments based on the number of employees, or users based on their date of registration.
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1 Apr 2021
Jakub Romanowski
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.
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1 Apr 2021
LearnSQL.com Team
New Monthly SQL Practice for April 2021!
Are you ready to use SQL skills to write queries that resolve business problems? Give it a try in the new Monthly SQL Practice on LearnSQL.com. The April SQL Practice is for people with a basic level of SQL proficiency. You will test your SQL skills based on data about an apartment rental agency in Chicago, USA. If this is the first time you’ve come across our Monthly SQL Practices, you should know that LearnSQL.
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31 Mar 2021
Andrew Bone
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.
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26 Mar 2021
Dorota Wdzięczna
How to Install MS SQL Server 2019 on Windows
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.
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25 Mar 2021
Jakub Romanowski
Is MS SQL Server Still Worth Learning in 2024?
Updated on: March 10, 2024 MS SQL Server is an in-demand skill in today’s job market. Should you learn MS SQL Server in 2024? In this article, I’ll answer this question. Thinking about whether you should dive into Microsoft SQL Server in 2024 – especially with so many free database alternatives available? MS SQL Server has been a go-to for handling data for ages, thanks to its solid features and reliability.
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