UNION
Combines results from multiple SELECT statements. UNION DISTINCT removes duplicate rows, while UNION ALL does not remove them. UNION is equivalent to UNION DISTINCT.
Syntax
SELECT ... UNION [ALL | DISTINCT] SELECT ... [UNION [ALL | DISTINCT] SELECT ...]
Remarks
The first and all subsequent
SELECTstatements must select the same number of columns.
Examples
SELECT * FROM table_a UNION ALL SELECT * FROM table_b; SELECT * FROM table_a UNION SELECT * FROM table_b;