在Oracle中，可以利用count()函数来查询重复字段，语法为“select * from 表名 where 字段 in(select 字段 from 表名 group by 字段 having count(字段) >1)”。

本教程操作环境：Windows10系统、Oracle 11g版、Dell G3电脑。

Oracle怎样查询重复字段

1、查找表中多余的重复记录，重复记录是根据单个字段（userCode）来判断

select 
* 
from 
user
where 
userCode
in 
(select  userCode  from  user group by  userCode having count (userCode) > 1)

2、删除表中多余的重复记录，重复记录是根据单个字段（userCode）来判断，只留有rowid最小的记录

delete from 
user 
where 
userCode 
in 
(select userCode from user group by  userCode having count (peopleId) > 1)
and rowid not in 
(select min(rowid) from   user group by userCode having count(userCode)>1)

3、查找表中多余的重复记录（多个字段）

select 
* 
from 
user a
where 
(a.userCode,a.userName) 
in  
(select userCode,userName from user group by userCode,userName 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 
user a
where
(a.userCode,a.userName) 
in   
(select userCode,userName from user group by userCode,userName having count(*) > 1)
and rowid not in 
(select min(rowid) from user group by userCode,userName 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 
user a
where 
(a.userCode,a.userName)  
in   
(select userCode,userName from user group by userCode,userName having count(*) > 1)
and rowid not in 
(select min(rowid) from user group by userCode,userName having count(*)>1)

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