oracle查找重复记录，去除重复记录

转载自http://blog.163.com/aner_rui/blog/static/12131232820105901451809/

SELECT *
FROM t_info a
WHERE ((SELECT COUNT(*)
          FROM t_info
          WHERE Title = a.Title) > 1)
ORDER BY Title DESC

一。查找重复记录

1。查找全部重复记录

Select * From 表 Where 重复字段 In (Select 重复字段 From 表 Group By 重复字段 Having Count(*)>1)

2。过滤重复记录(只显示一条)

Select * From HZT Where ID In (Select Max(ID) From HZT Group By Title)

注：此处显示ID最大一条记录

二。删除重复记录

1。删除全部重复记录（慎用）

Delete 表 Where 重复字段 In (Select 重复字段 From 表 Group By 重复字段 Having Count(*)>1)

2。保留一条（这个应该是大多数人所需要的 ^_^）

Delete HZT Where ID Not In (Select Max(ID) From HZT Group By Title)

注：此处保留ID最大一条记录

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

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）

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)

补充：

有两个以上的重复记录，一是完全重复的记录，也即所有字段均重复的记录，二是部分关键字段重复的记录，比如Name字段重复，而其他字段不一定重复或都重复可以忽略。

 

1、对于第一种重复，比较容易解决，使用

select distinct * from tableName

 

就可以得到无重复记录的结果集。

 

如果该表需要删除重复的记录（重复记录保留1条），可以按以下方法删除

select distinct * into #Tmp from tableName

drop table tableName

select * into tableName from #Tmp

drop table #Tmp

 

发生这种重复的原因是表设计不周产生的，增加唯一索引列即可解决。

 

2、这类重复问题通常要求保留重复记录中的第一条记录，操作方法如下

 

假设有重复的字段为Name,Address，要求得到这两个字段唯一的结果集

select identity(int,1,1) as autoID, * into #Tmp from tableName

select min(autoID) as autoID into #Tmp2 from #Tmp group by Name,autoID

select * from #Tmp where autoID in(select autoID from #tmp2)

 

最后一个select即得到了Name，Address不重复的结果集（但多了一个autoID字段，实际写时可以写在select子句中省去此列）