mysql如何删除重复记录

方法有很多，除了最简便的，

alter ignore table 表名 add UNIQUE index(字段名);

然后再将索引drop掉，这个方法外。

更加中规中矩的方法也是有的。。

比如我在网上搜到的：

delete from people
where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)
and id not in (select min(id) from people group by peopleId having count(peopleId )>1)

这个看起来好像很有道理，但是执行的时候就会报错。。You can't specify target table 'people' for update in FROM clause。

原因就是上面的那一条SQL，删除和查询操作都是针对同一张表的。。MYSQL是不允许这样做滴。

这样就可以了

delete from people
where peopleId in (select peopleId from(select id,peopleId from people) as a group by peopleId having count(peopleId) > 1)
and id not in (select min(id) from (select id,peopleId from people) as b group by peopleId having count(peopleId )>1)

简单一点的可以这样写

delete from id where Id not in (select min(Id) from(select id,peopleId from people)as a GROUP by peopleId );

粗体部分就是把一张表转换成了一个提取表（derived table)，从而解决了问题，需要注意的是后面那个as 别名，不能省略，否则会报错"Every derived TABLE must have its own alias“。

巴特西

mysql如何删除重复记录

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