sql如何去重查询-木庄网络博客

本文摘自PHP中文网，作者coldplay.xixi，侵删。

sql去重查询的方法：重复记录根据单个字段peopleId来判断，使用语句删除，代码为【where peopleId in (select peopleId from people group by peopleId 】。

sql去重查询的方法：

sql 单表/多表查询去除重复记录

单表distinct

多表group by

group by 必须放在 order by 和 limit之前，不然会报错

1、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

1 2	`select * from people` `where peopleId in (select peopleId from people group by peopleId having` `count(peopleId) > 1)`

2、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

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)

3、查找表中多余的重复记录（多个字段）

1 2	`select * from vitae a` `where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having` `count(*) > 1)`

4、删除表中多余的重复记录（多个字段），只留有rowid最小的记录

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)

5、查找表中多余的重复记录（多个字段），不包含rowid最小的记录

select * 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)

(二)

比方说

在A表中存在一个字段“name”，

而且不同记录之间的“name”值有可能会相同，

现在就是需要查询出在该表中的各记录之间，“name”值存在重复的项；