MySQL 删除数据库中重复数据(以部分数据为准)
where tel in (select min(dpxx_id) from zqzrdp group by tel having count(tel)>1);
执行,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。
难倒只能分步操作,蛋疼
以下是网友写的,同样是坑爹的代码,我机器上运行不了。
1. 查询需要删除的记录,会保留一条记录。
代码如下 | 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. 删除重复记录,只保留一条记录。注意,subject,RECEIVER 要索引,否则会很慢的。
代码如下 | 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. 查找表中多余的重复记录,重复记录是根据单个字段(peopleId)来判断
代码如下 | 复制代码 |
select * from people |
4. 删除表中多余的重复记录,重复记录是根据单个字段(peopleId)来判断,只留有rowid最小的记录
代码如下 | 复制代码 |
delete from people |
5.删除表中多余的重复记录(多个字段),只留有rowid最小的记录
代码如下 | 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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