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
SELECT
statements 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;
SELECT * FROM id_t UNION ALL SELECT * FROM id_t2; **** +------+----------------------------------------------------------------------------+ | a | b | +------+----------------------------------------------------------------------------+ | 1 | 0xE82C75FA86974BE7903270F4353D865C | | 1 | 0x31343865306665352D666666322D346363362D383634622D313838303637313135653236 | +------+----------------------------------------------------------------------------+