如何删除表中的重复记录？

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--测试数据
/*-----------------------------
select*fromtt
-----------------------------*/
id         pid        
----------------------
1          1
1          1
2          2
3          3
3          3
3          3

（所影响的行数为6行）

首先，如何查询table中有重复记录
select*,count(1)asrownum
fromtt
groupbyid,pid
havingcount(1)>1
id         pid        rownum     
---------------------------------
1          1          2
3          3          3

（所影响的行数为2行）

方法一:使用distinct和临时表
ifobject_id('tempdb..#tmp')isnotnull
droptable#tmp
selectdistinct*into#tmpfromtt
truncatetablett
insertintottselect*from#tmp

方法二:添加标识列
altertablettaddNewIDintidentity(1,1)
go 
deletefromtt whereexists(select1fromttawhere a.newid>tt.newidandtt.id=a.idandtt.pid=a.pid)
go
altertablettdropcolumnNewID
go

--测试结果
/*-----------------------------
select*fromtt
-----------------------------*/
id         pid        
----------------------
1          1
2          2
3          3

（所影响的行数为3行）

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