MSSQL如何删除表中的重复记录？

--测试数据
[quote]
/*-----------------------------

select * from tt

-----------------------------*/

id pid

----------- -----------

1 1

1 1

2 2

3 3

3 3

3 3
[/quote]
（所影响的行数为 6 行）
首先，如何查询table中有重复记录
[quote]
select *,count(1) as rownum

from tt

group by id, pid

having count(1) > 1

id pid rownum

----------- ----------- -----------

1 1 2

3 3 3
[/quote]
（所影响的行数为 2 行）
方法一:使用distinct和临时表
[quote]
if object_id('tempdb..#tmp') is not null

drop table #tmp

select distinct * into #tmp from tt

truncate table tt

insert into tt select * from #tmp
[/quote]
方法二:添加标识列
[quote]
alter table tt add NewID int identity(1,1)

go

delete from tt where exists(select 1 from tt a where a.newid>tt.newid and tt.id=a.id and tt.pid=a.pid)

go

alter table tt drop column NewID

go


/*注，oracle中由于有伪列rowid则更简单，可以直接用rowid*/

/*

delete from tt where exists(select 1 from tt a where a.rowid>tt.rowid and tt.col1=a.col1 and tt.col2=a.col2)

*/
[/quote]
--测试结果
[quote]
/*-----------------------------

select * from tt

-----------------------------*/

id pid

----------- -----------

1 1

2 2

3 3
[/quote]
（所影响的行数为 3 行）