mysql清除表中的重复数据
例子:我这是用户角色关联表,根据用户id和角色id确认唯一一条数据
1:先查出重复数据,可以根据自己的需求更换sql中的字段,或者增加条件
SELECT
a.ROLE_ID,
a.USER_ACCOUNT_ID
FROM
cof_role_user a
WHERE
( a.ROLE_ID, a.USER_ACCOUNT_ID ) IN ( SELECT role_id, USER_ACCOUNT_ID FROM cof_role_user GROUP BY role_id, USER_ACCOUNT_ID HAVING count( * ) > 1 )
ORDER BY
USER_ACCOUNT_ID
2:删除重复数据并保留一条数据,id是主键,必须保留一条数据
delete from cof_role_user
where (role_id,USER_ACCOUNT_ID)
in (SELECT * from
(select role_id,USER_ACCOUNT_ID from cof_role_user group by role_id,USER_ACCOUNT_ID having count(*) > 1)
a)
and id
not in (SELECT * from
(select min(id) from cof_role_user group by role_id,USER_ACCOUNT_ID having count(*)>1) b
)