mysql - 如何删除MySQL表中的重复行？

Question

我正在使用以下查询，这是我从另一个 stackoverflow 问题中看到的，但出现错误。

delete from mytable
 where myid not in (
    select max(myid)
      from mytable
group by myid2)

错误:

#1093 - Table 'mytable' is specified twice, both as a target for 'DELETE' and as a separate source for data

编辑2:

我也尝试过这个查询:

delete from mytable
 where myid in (
    SELECT
    myid, COUNT(*)
FROM
    mytable
GROUP BY
    myid2
HAVING 
    COUNT(*) > 1)

并收到此错误:

#1241 - Operand should contain 1 column(s)

Answer 1

在 MySQL 中，您需要使用 JOIN 来实现此目的。我想你的意思是这样的:

delete t
   from mytable t left join
        (select max(myid) as myid
         from mytable
         group by myid2
        ) tt
        on t.myid = tt.myid
   where tt.myid is null;

Where ? 是您真正想要分组的依据。您的版本不会删除任何内容，因为 group by 和 max() 使用同一列。