Articles Cookbook
9 Nov 2021
Himanshu Kathuria

How to Write a WHERE Clause in SQL

We explain how to use the SQL WHERE clause with practical examples. If you have just started learning SQL and want to know how to retrieve or work with only a specific portion of the data stored in your tables, then this article is for you! What is WHERE Clause in SQL? The SQL WHERE clause filters records based on specific conditions; it allows you to selectively retrieve, modify, or delete data in a database.
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5 Nov 2021
Karolina Niewiarowska

How Can SQL Developers Remember Everything They Learn?

Are you at the beginning of your SQL journey? Congratulations, great choice! But you may find the knowledge you gain leaks with time. Find out what SQL developers do to remember everything they learn for a long time. If you learn SQL, the road to the expert level is long, winding, and bumpy. But don't worry – we've all been through it. You know perfectly well it's worth it.
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3 Nov 2021
Andrew Bone

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.
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29 Oct 2021
Ignacio L. Bisso

What Is a Rolling Average and How Do You Compute It in SQL?

In this article, we will show three different examples of using SQL to calculate rolling averages. Learn this and you will take an important step in your SQL growth! A rolling average is a metric that allows us to find trends that would otherwise be hard to detect. It is usually based on time series data. In SQL, we calculate rolling averages using window functions. First, let’s talk about what rolling averages are and why they’re useful.
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28 Oct 2021
Jakub Romanowski

Top 5 Linux Distributions for SQL

The world is divided into Linux lovers and people who have never tried it before. Still working on Windows or macOS? Do you want to learn SQL? Do you know a large proportion of IT professionals use Linux? It's not a coincidence. But which Linux distribution should you choose for learning SQL? Here's my factsheet to help answer that question.   Linux Distribution: What Is It? What is a Linux distribution?
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27 Oct 2021
Kateryna Koidan

SQL Date and Time Functions in 5 Popular SQL Dialects

Are you confused by all the date and time functions used across different SQL dialects? In this article, I summarize the date and time data types used in PostgreSQL, Oracle, SQLite, MySQL, and T-SQL. I also provide examples with the key SQL date and time functions used across these dialects. It’s time to become date and time gurus! Do you want to calculate how often employees are running late for work?
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22 Oct 2021
Jakub Romanowski

New Window Functions Practice Set Is Here!

Have you learned the SQL window functions? Or maybe, you forgot when and how to use them correctly? Are you preparing for an advanced SQL job interview? You've come to the right place! This is the new Window Functions Practice Set. This is very good news for all SQL learners and database professionals who want to improve their skills. The LearnSQL.com Team is proud to present the new Window Functions Practice Set!
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21 Oct 2021
Himanshu Kathuria

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.
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20 Oct 2021
Marcin Koryszewski

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.
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19 Oct 2021
Tihomir Babic

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.
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