Oracle 查询重复数据

 

 

SQL重复记录查询方法 
2008年08月14日 星期四 21:01 SQL重复记录查询 
 
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)

 (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；

Select Name,Count(*) From A Group By Name Having Count(*) > 1 

如果还查性别也相同大则如下: 

Select Name,sex,Count(*) From A Group By Name,sex Having Count(*) > 1

 (三) 方法一 

declare @max integer,@id integer 
declare cur_rows cursor local for select 主字段,count(*) from 表名 group by 主字段 having 
count(*) >； 1 open cur_rows 
fetch cur_rows into @id,@max while @@fetch_status=0 begin 
select @max = @max -1 set rowcount @max 
delete from 表名 where 主字段 = @id fetch cur_rows into @id,@max end 
close cur_rows set rowcount 0   

方法二 
  有两个意义上的重复记录，

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）
(四)查询重复 

select * from tablename where id in ( select id from tablename group by id having count(id) > 1 )