MySQL 删除数据库中反复数据（以部分数据为准）

时间：2023-03-09 00:27:42
MySQL 删除数据库中反复数据（以部分数据为准）

delete from zqzrdp

where tel  in (select min(dpxx_id) from  zqzrdp  group by tel  having count(tel)>1);

运行，报错MySQL 删除数据库中反复数据（以部分数据为准）

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异常意为：你不能指定目标表的更新在FROM子句。傻了。MySQL 这样写，不行，让人郁闷。

难倒仅仅能分步操作，蛋疼

下面是网友写的。相同是坑爹的代码，我机器上执行不了。

1. 查询须要删除的记录，会保留一条记录。

 代码例如以下 复制代码

select a.id,a.subject,a.RECEIVER from test1 a left join (select c.subject,c.RECEIVER ,max(c.id) as  bid from test1 c where status=0 GROUP BY RECEIVER,SUBJECT having count(1) >1) b on a.id< b.bid where  a.subject=b.subject and a.RECEIVER = b.RECEIVER and a.id
< b.bid

2. 删除反复记录，仅仅保留一条记录。注意。subject,RECEIVER 要索引。否则会非常慢的。

 代码例如以下 复制代码

delete a from test1 a, (select c.subject,c.RECEIVER ,max(c.id) as  bid from test1 c where status=0 GROUP BY RECEIVER,SUBJECT having count(1) >1) b where a.subject=b.subject and a.RECEIVER = b.RECEIVER and a.id < b.bid;

3. 查找表中多余的反复记录。反复记录是依据单个字段（peopleId）来推断

 代码例如以下 复制代码

select * from people

where peopleId in (select  peopleId  from  people  group  by  peopleId  having  count(peopleId) > 1)

4. 删除表中多余的反复记录，反复记录是依据单个字段（peopleId）来推断。仅仅留有rowid最小的记录

 代码例如以下 复制代码

delete from people 

where peopleId  in (select  peopleId  from people  group  by  peopleId   having  count(peopleId) > 1)

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

5.删除表中多余的反复记录（多个字段）。仅仅留有rowid最小的记录

 代码例如以下 复制代码
delete from vitae a

where (a.peopleId,a.seq) in  (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)

and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)

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