Question

我的数据库中有一个表（Final），我想删除除了
之外的所有重复行那些有NULL值的人;
我尝试了以上内容：

 DELETE FROM Final 
  WHERE event_id NOT IN (SELECT MIN(event_id) AS MinID 
                           FROM (SELECT * FROM Final) as x 
                          GROUP BY event_name
                            AND event_name IS NOT NULL)

但没有用。

修改

我的桌子似乎是：

id |珊瑚
1 | NULL
2 | 1
3 | 1＆lt; - DELETE
4 | 2
5 | NULL＆lt; - 保持原样 6 | 1＆lt; -DELETE

Answer 1

加入桌子怎么样？

DELETE  a
FROM    Final a
        LEFT JOIN
        (
            SELECT  Event_name, MIN(Event_ID) MIN_ID
            FROM    Final
            WHERE   Event_name IS NOT NULL
            GROUP   BY Event_name
        ) b ON a.Event_name = b.Event_name AND
                a.Event_ID = b.MIN_ID
WHERE   a.Event_name IS NOT NULL AND 
        b.Event_name IS NULL

Answer 2

只需将AND event_name IS NOT NULL部分移动到主子查询：

DELETE FROM Final 
  WHERE event_id NOT IN (SELECT MIN(event_id) AS MinID 
                           FROM (SELECT * FROM Final) as x 
                          GROUP BY event_name)
    AND event_name IS NOT NULL

MySQL删除除NULL以外的重复行

2 个答案: