sql 删除重复数据性能比较
--2(速度第二)
delete m from tb_toupiao1 m where id not in
(select min(id) from tb_toupiao1 group by convert(varchar(16),addtime,120),usid,ptid)
--3(速度第三)
delete from tb_toupiao2 where id not in
(select min(id) from tb_toupiao2 group by convert(varchar(16),addtime,120),usid,ptid)
--1(速度第一)
delete m from tb_toupiao3 m where id not in
(select min(id) from tb_toupiao3 n where m.addtime = n.addtime and m.usid = n.usid and m.ptid=n.ptid )
如上sql,都是删除重复记录的sql,但是执行起来速度却相差很大,哪位仁兄来解释下啦。谢过 ~