常用数据库操作

1、去除重复记录

delete from device_data where id not in

(select t2.id from

(select max(t1.id) id from device_data t1 GROUP BY t1.psItemNo, t1.address, t1.DataDate) t2)

注：in条件需要建立第三方表t2，否则mysql会报错：[Err] 1093 - You can't specify target table 's' for update in FROM clause。

即如下语句错误：

delete from device_data where id not in

(select max(t1.id) id from device_data t1 GROUP BY t1.psItemNo, t1.address, t1.DataDate)