select F.uid, ifnull(A.level,0) as level, ifnull(B.meileage,0) as mileage, ifnull(complaint_cnt,0) as complaint_cnt from (select uid from A UNION select uid from B UNION select uid from C) as F left join A on A.uid = F.uid left join B on B.uid = F.uid left join C on C.uid = F.uid