MySQL 删除数据库中反复数据（以部分数据为准）

Posted 2020-09-21 zsychanpin

delete from zqzrdp 

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

运行，报错

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)