Articles Cookbook
3 Dec 2020
Kateryna Koidan

How Do You Write a SELECT Statement in SQL?

SQL is a language to communicate with relational databases, and the SELECT statement is the first thing you’ll learn when you start using SQL. In this article, you’ll learn how to write SELECT statements, from the basics to more advanced. What Is SQL? SQL stands for “Structured Query Language.” It has a long history that started in the 1970s. Being the standard for communication with relational databases, it has maintained its popularity.
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2 Dec 2020
Agnieszka Kozubek-Krycuń

SQL Technologies Are More Common Than You Think

Where is SQL being used today? The answers might surprise you! (Hint: SQL technology is basically everywhere.) Is it worth learning SQL? After all, the language was created in the 1970s. Is it still relevant today? The list of technologies that support SQL is very long – and it’s growing. Read on to find out what kinds of programs use SQL. SQL in Databases Relational Databases = SQL Databases It’s no surprise that SQL is used in relational databases.
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1 Dec 2020
LearnSQL.com Team

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?
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27 Nov 2020
Ignacio L. Bisso

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.
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26 Nov 2020
Kateryna Koidan

Aggregate Functions vs Window Functions: A Comparison

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.
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25 Nov 2020
Tihomir Babic

How to Find All Employees Under Each Manager in SQL

Have you ever been tasked with building an organizational chart – i.e. finding the employees under each manager in a company? In SQL, you can do that easier than you think! This article will show you how to get the answer using a recursive query. In the business world, it’s a very common task to list all the subordinate employees for a given manager. Is doing this hard enough to warrant a whole article?
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24 Nov 2020
Jakub Romanowski

SQL in the Open-Source World

Did you know there are free, open-source databases that use SQL? In this article, I'll show you which open-source database solutions can meet your needs. Ever wonder why many people still use paid programs when the same things can be done with free options? Personally, I am an avid supporter of the open-source movement. For years, I have been trying to apply and promote such solutions and support an active community around them.
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20 Nov 2020
Adrian Więch

How To Learn The SELECT Statement in SQL

When you think about learning SQL, one of the first things you come across is the SELECT statement. Selecting information is arguably the most important SQL feature. In this article, we’ll demonstrate the typical use cases for SQL SELECT with practical examples. Read this article if you’re a beginner database user and would like to know what SELECT can do for you. SQL, or Structured Query Language, is the programming language the IT world uses to communicate with databases.
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19 Nov 2020
Martyna Sławińska

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.
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17 Nov 2020
Agnieszka Kozubek-Krycuń

The History of SQL – How It All Began

Who created SQL and why? Find out in this article! Here’s a brief history of SQL, starting with its foundational concept: the database. Ted Codd and the Relational Data Model The first computer databases appeared in the late 1960s. This was an important area of research at the time. Many computer scientists were focused on improving how databases work. One of them was Edgar Frank (Ted) Codd, an English computer scientist employed at IBM.
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