SQL UNION Operator

The UNION operator is used to combine the result-set of two or more SELECT statements.

Notice that each SELECT statement within the UNION must have the same number of columns. The columns must also have similar data types. Also, the columns in each SELECT statement must be in the same order.

SQL UNION Syntax

SELECT column_name (s) FROM table_name1

UNION

SELECT column_name (s) FROM table_name2

*The UNION operator select only distinct values by default. To allow duplicate values, use UNION ALL.

SQL UNION ALL Syntax
SELECT column_name (s) FROM table_name1
UNION ALL
SELECT column_name (s) FROM table_name2