**UNION** is an operator that concatenates results of different SQL queries:

--do not run this query
SELECT columns FROM table1
UNION
SELECT columns FROM table2
UNION
...
SELECT columns FROM tableN

There is also an operator **UNION ALL**, and the difference is that **UNION** returns distinct values, unlike  **UNION ALL**.

Requirements for using **UNION** operators:
 - number of columns in `SELECT` should be the same
 - data types and order of columns should be the same

If you're an expert in creating queries for a single table, improve your knowledge! Let's start accessing and manipulating two and more tables. During the course, you'll learn how to work with special statements, what is the join and how to use it, and also will practice a lot!

We shall take a look at the database we'll work with and how we can create a query inside another query.

Learn how to join and work with multiple tables.

Try creating queries with no limits on how you should do that. Use all your knowledge from previous chapters!

SQL Union

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