在oracle中，可以利用count()函数配合select查询语句来查询重复的数据，语法为“select userCode from user group by userCode having count(userCode)>1”。
本教程操作环境：Windows10系统、Oracle 11g版、Dell G3电脑。
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)推荐教程：《Oracle视频教程》
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