Skip navigation
Courses
Pricing
For Students
SQL Library
Articles
Cookbook
Cheat Sheets
For Beginners
Best Way to Learn SQL
SQL Primer
Flashcards
About Our Courses
Guides
150+ SQL Practice Exercises
100+ SQL Interview Questions
SQL Interview Cheat Sheet
GROUP BY and Aggregate Functions Guide
SQL JOINs Guide
Window Functions Guide
Numeric Functions Guide
String Functions Guide
Common Table Expressions
Log in
Create free account
fullName
User profile menu open
Open user profile menu
fullName
Dashboard
My Profile
Payment & Billing
Log out
MENU
CLOSE
Courses
Pricing
For Students
Articles
Cookbook
Cheat Sheets
Best Way to Learn SQL
SQL Primer
Flashcards
About Our Courses
150+ SQL Practice Exercises
100+ SQL Interview Questions
SQL Interview Cheat Sheet
GROUP BY and Aggregate Functions Guide
SQL JOINs Guide
Window Functions Guide
Numeric Functions Guide
String Functions Guide
Common Table Expressions
Dashboard
My Profile
Payment & Billing
Log in
Create free account
Log out
Articles
Cookbook
12 May 2021
Kamila Ostrowska
The Best Books for Data Engineers
Getting tired of the endless screen glare? It might be a good time to switch to a book. Dive into our selected list of books for data engineers, perfect for expanding your insights on databases. It’s a refreshing change from the digital routine! Last time, I shared a list of the best books to learn SQL. This time, I want to introduce a few books for data engineers. They are worth reading and will help you learn more about databases.
Read more
7 May 2021
Zahin Rahman
What Is the WITH Clause in SQL?
In this article, you will learn about the SQL WITH clause, also known as common table expression (CTE). We will go over some examples to demonstrate some of their use cases in light of their benefits. Today, I'm here to guide you through the intricacies of the SQL WITH clause, commonly known as Common Table Expression (CTE). If you've faced challenges with lengthy and complex SQL queries, this article will be particularly useful.
Read more
6 May 2021
Jakub Romanowski
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.
Read more
5 May 2021
Kateryna Koidan
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.
Read more
4 May 2021
LearnSQL.com Team
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.
Read more
29 Apr 2021
Ignacio L. Bisso
Why Do You Need a Primary Key in a Database Table?
What is a primary key and why is it so important in SQL? Find out in this article. Primary keys are a central element in SQL databases. They provide a unique value that can identify a specific row in a table, which opens up a lot of other benefits. This article covers what a primary key is, how it works, and how to use it in an SQL database.
Read more
28 Apr 2021
LearnSQL.com Team
Breaking With Filing Cabinets: The History of PostgreSQL
This July, PostgreSQL turns 25. It has had an extensive influence on computing. Thanks to PostgreSQL, the world said “Goodbye!” to filing cabinets as the standard for storing and processing data. So, who created PostgreSQL, and how has it changed over the decades? There are quite a few PostgreSQL enthusiasts among my colleagues at LearnSQL.com. It is simply a great database solution. Why? It is free and open-source. So, you can use it for free, even for commercial uses.
Read more
27 Apr 2021
Martyna Sławińska
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.
Read more
23 Apr 2021
Andrew Bone
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.
Read more
21 Apr 2021
Andrew Bone
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.
Read more
««
«
1
2
3
54
55
56
89
»
»»