SELECT UNION Syntax¶
Common Syntax¶
SELECT ...UNION [ALL | DISTINCT]
SELECT ...[UNION [ALL | DISTINCT] SELECT ...]
Example¶
select userid from user union select orderid from ordertbl order by userid;
select userid from user union (select orderid from ordertbl group by orderid) order by userid;
Syntax Restrictions¶
SELECT statements in UNION do not support duplicate column names.