Mysql SQL-删除表X中的所有重复项

我尝试从表fe_用户中获取所有冗余UID的列表，然后运行DELETE命令删除它们

e、 g.我有以下表格供用户使用：

uid | pid | username
--------------
1   | 100 |  hans
2   | 100 |  karl
3   | 100 |  franz
4   | 100 |  karl
5   | 100 |  hans

这是我选择所有重复项的方式：

SELECT * FROM fe_users
WHERE uid NOT IN (
    SELECT uid  
    FROM fe_users
    WHERE pid=100
    GROUP BY username
    HAVING COUNT(username) > 1
)
AND username IN (
    SELECT username 
    FROM fe_users
    WHERE pid=100
    GROUP BY username
    HAVING COUNT(username) > 1
)

返回：

现在我必须删除它们

尝试1：

提示：刚才用DELETE替换了上面的SELECT查询

答复：

无法在FROM子句中为更新指定目标表“fe\U users”

尝试2

所以我试着再使用一个select，如中所建议的

答复：

“从pid=0 GROUP BY的fe_用户中选择uid”附近的语法错误 4号线的usernam

我不知道我如何才能做到这一点，我想知道MySQL开发人员在实现这一毫无意义的限制时会怎么想

---

我必须使用PHP删除它吗？

您的查询似乎比需要的更复杂。我会选择：

delete u
    from fe_users u join
         fe_users u2
         on u.pid = u2.pid and u.username = u2.username and
            u2.uid > u.uid
    where u.pid = 100;

---

这将删除具有相同pid和用户名且uid较大的行的所有行。您可以通过将“删除u”更改为“选择u.*”来获取列表。

我的第二次尝试包含了错误输出所述的语法错误。 我错过了，还有其他一些错误。这是工作查询：

DELETE FROM fe_users
WHERE uid NOT IN (
    SELECT uid FROM (
        SELECT uid
        FROM fe_users
        WHERE pid=100
        GROUP BY username
        HAVING COUNT(username) > 1
        ) As uid
    )
AND username IN (
    SELECT username FROM (
        SELECT username 
        FROM fe_users
        WHERE pid=100
        GROUP BY username
        HAVING COUNT(username) > 1
        ) AS username
    )
AND pid=100

---

我希望MySQL开发人员能够解决这一问题，这样我们就不需要添加不必要的选择。

删除*号，它不在您显示的查询中，但错误消息显示您在实际查询中使用了它。删除查询没有*两个子查询的可能重复项都缺少from子句，即您有SELECT uid SELECT uid from…，它应该是SELECT uid from SELECT uid from。。。。话虽如此，戈登的回答却不那么冗长，因此更易于阅读和维护，最终结果完全相同。@GarethD，你是对的，谢谢！

DELETE FROM fe_users
WHERE uid NOT IN (
    SELECT uid (
        SELECT uid
        FROM fe_users
        WHERE pid=100
        GROUP BY username
        HAVING COUNT(username) > 1
        )
    ) AS uid
AND username IN (
    SELECT username (
        SELECT username 
        FROM fe_users
        WHERE pid=100
        GROUP BY username
        HAVING COUNT(username) > 1
        )
    ) AS username;

delete u
    from fe_users u join
         fe_users u2
         on u.pid = u2.pid and u.username = u2.username and
            u2.uid > u.uid
    where u.pid = 100;

DELETE FROM fe_users
WHERE uid NOT IN (
    SELECT uid FROM (
        SELECT uid
        FROM fe_users
        WHERE pid=100
        GROUP BY username
        HAVING COUNT(username) > 1
        ) As uid
    )
AND username IN (
    SELECT username FROM (
        SELECT username 
        FROM fe_users
        WHERE pid=100
        GROUP BY username
        HAVING COUNT(username) > 1
        ) AS username
    )
AND pid=100