SELECT Pic1 FROM T1 WHERE UserId=5 UNION ALL SELECT Pic2 FROM T1 WHERE UserId=5 UNION ALL SELECT Pic3 FROM T1 WHERE UserId=5 UNION ALL SELECT Pic1 FROM T2 WHERE UserId=5 UNION ALL SELECT Pic2 FROM T2 WHERE UserId=5 UNION ALL SELECT Pic3 FROM T2 WHERE UserId=5 UNION ALL SELECT Pic1 FROM T3 WHERE UserId=5 UNION ALL SELECT Pic2 FROM T3 WHERE UserId=5 UNION ALL SELECT Pic3 FROM T3 WHERE UserId=5 UNION ALL ....我是这样做的,但觉得性能不够好,没有更好办法吗?
试试 select * from ( select pic1 from t1 union all select pic2 from t1 .... )t where useid=5
SELECT Pic2 FROM T1 WHERE UserId=5 UNION ALL
SELECT Pic3 FROM T1 WHERE UserId=5 UNION ALL
SELECT Pic1 FROM T2 WHERE UserId=5 UNION ALL
SELECT Pic2 FROM T2 WHERE UserId=5 UNION ALL
SELECT Pic3 FROM T2 WHERE UserId=5 UNION ALL
SELECT Pic1 FROM T3 WHERE UserId=5 UNION ALL
SELECT Pic2 FROM T3 WHERE UserId=5 UNION ALL
SELECT Pic3 FROM T3 WHERE UserId=5 UNION ALL
....我是这样做的,但觉得性能不够好,没有更好办法吗?
select
*
from
(
select pic1 from t1
union all
select pic2 from t1
....
)t
where
useid=5