Question

Am试图使用带有where子句的select查询来获取记录，显示id重复记录，然后我想按createdAt字段对其进行过滤。

在运行以下查询并获得如下结果时：

select * from security_development.user_requests
where
fully_approved = 1 and user_request_role=4

请找到结果

createdAt           User_request_name fully_approved user_request_role
2019-02-22 18:57:08  dealerAdmin        1               4
2019-02-24 08:57:08  ask1               1               4
2019-02-25 12:20:22  dealerAdmin        1               4

如果我尝试通过使用User_request_name作为子查询来仅避免重复的max(creaTed_at)，

select * from security_development.user_requests
where fully_approved =1 and user_request_role=4
created_at = 
(select max(creaTed_at) from security_development.user_requests group by user_request_name having count(user_request_name) > 1 )

然后得到以下结果

createdAt           User_request_name fully_approved user_request_role
2019-02-25 12:20:22  dealerAdmin        1               4

但希望获得以下结果

createdAt           User_request_name fully_approved user_request_role
2019-02-24 08:57:08  ask1               1               4
2019-02-25 12:20:22  dealerAdmin        1               4

Answer 1

您可以使用相关子查询

select t1.* from security_development.user_requests t1
where
fully_approved = 1 and user_request_role=4
and createdAt=( select max(createdAt) 
              from security_development.user_requests t2
                where t1.User_request_name=t2.User_request_name)

Answer 2

与问题不完全相同

要删除保存最新的现有重复项，请执行以下操作：

DELETE t1 FROM user_requests t1
INNER JOIN user_requests t2 
WHERE t1.createdAt < t2.createdAt AND t1.user_request_name = t2.user_request_name

为防止插入重复的User_request_name：

Alter table user_requests
add unique key (User_request_name);

仅由创建的Mysql查询过滤的重复记录

2 个答案: