An UNION operator must have an equal number of columns in the SELECT:
(SELECT *, t.table_id, t.title, t.description FROM TABLE t LEFT JOIN jointable jt ON t.table_id=jt.table_id WHERE t.status=1 GROUP BY t.table_id ORDER BY description) UNION (SELECT *, t.table_id, t.title, t.description FROM TABLE t LEFT JOIN jointable jt ON t.table_id=jt.table_id WHERE t.user_id=1) |