MySql如何删除所有多余的重复数据
- 需要处理的数据,如:
- 出现重复的数据,如:
- 先用SELECT查询看看结果:
-- 方法一
SELECT * FROM t_user WHERE user_name IN (
SELECT user_name FROM t_user GROUP BY user_name HAVING COUNT(1)>1
)
AND id NOT IN (
SELECT MIN(id) FROM t_user GROUP BY user_name HAVING COUNT(1)>1
)
- 方法一查询出的所有多余的重复记录:
-- 方法二
SELECT * FROM t_user WHERE id NOT IN (
SELECT MIN(id) FROM t_user GROUP BY user_name
)
- 1
- 2
- 3
- 4
- 方法二查询出的所有多余的重复记录(与