sql删除数据库中的重复记录方法

来源：爱go旅游网

我们分享了二个实现，来告诉你如何把数据表中重复记录的记录给删除只保留一条，这种方法风险性比较大，另一种方法利用临时表，这种方法相对上种要好些。

删除中的重复记录（且仅保留一条有效记录）示例-

代码如下

create table A
(
userID int identity(1,1),
userName varchar(20),
userPwd varchar(20),
userEmail varchar(50)
)
insert into A(userName,userpwd) 'qin','qin' union all select 'qin','qin1' union all select 'qin','qin1'
select * from A

--method one
delete from A where userid not in(select min(userid) as userid from A group by username ,userpwd)

--method two
delete from A where exists (select * from A b where a.username = b.username and a.userpwd = b.userpwd and a.userid < b.userid)

--method three
delete from a where userid not in(select min(userid) from A b where a.username = b.username and a.userpwd = b.userpwd and a.userid > b.userID)

select * from A
drop table A

利用临时表方法

删除重复记录,将TABLE_NAME中的不重复记录保存到#TABLE_NAME中

代码如下
select distinct * into #table_name from table_name delete from table_name select * into table_name from #table_name drop table #table_name