SELECT t1.* FROM (
SELECT *,'1' AS bbs_id
FROM board1_cont
UNION SELECT *,'2' AS bbs_id
FROM board2_cont
UNION SELECT *,'3' AS bbs_id
FROM board3_cont
UNION SELECT *,'4' AS bbs_id
FROM board4_cont
) AS t1
LEFT JOIN member AS t2 ON t2.user_id = t1.user_id
WHERE 1 AND t1.b_level = '0' AND t1.bbs_id='3'
