SELECT FOR UPDATE with UNION should not need parenthesis

select id1 from t1 for update

union

select id2 from t2 for update

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'union

select id2 from t2 for update' at line 2

(select id1 from t1 for update) union (select id2 from t2 for update);