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SQL删除重复数据方法

时间:2015-03-04 09:46:16      阅读:141      评论:0      收藏:0      [点我收藏+]

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例如: 
id           name         value 
1               a                 pp 
2               a                 pp 
3               b                 iii 
4               b                 pp 
5               b                 pp 
6               c                 pp 
7               c                 pp 
8               c                 iii 
id是主键 
要求得到这样的结果 
id           name         value 
1               a                 pp 
3               b                 iii 
4               b                 pp 
6               c                 pp 
8               c                 iii

方法1
delete   YourTable   
where   [id]   not   in   ( 
select   max([id])   from   YourTable   
group   by   (name   +   value)) 

方法2
delete   a 
from   表   a   left   join( 
select   id=min(id)   fromgroup   by   name,value 
)b   on   a.id=b.id 
where   b.id   is   null 

 


查询及删除重复记录的SQL语句


(一)
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 "重复记录"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 )

 

SQL删除重复数据方法

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原文地址:http://www.cnblogs.com/zouhao/p/4312353.html

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