The SQL UNION Operator

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

• Every SELECT statement within UNION must have the same number of columns
• The columns must also have similar data types
• The columns in every SELECT statement must also be in the same order

UNION Syntax

UNION ALL Syntax

The UNION operator selects only distinct values by default. To allow duplicate values, use UNION ALL:

Note: The column names in the result-set are usually equal to the column names in the first SELECT statement.

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