What is the syntax of UNION operator in mysql

What is the UNION operator in mysql?

The MySQL UNION operator is used to combine the results of two or more SELECT statements into a result set.

Multiple SELECT statements will delete duplicate data.

UNION operator syntax:

SELECT column_name(s) FROM table1
UNION
SELECT column_name(s) FROM table2;

Note: The column name in the UNION result set is always equal to the first SELECT in UNION Column names in statements.

Usage example: Select all different countries (only different values) from the "Websites" and "app" tables

SELECT country FROM Websites
UNION
SELECT country FROM app
ORDER BY country;

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