删除表中重复记录，保留最小记录 OR 删除表中所有行重复记录

问题1：

 有表如下：

create Ta

(

   id int identity(1,1) not null,

   code varchar(10) null,

   num float null

)

insert Ta(code,num)

select  '001',100.00 union all

select  '001',100.00 union all

select  '001',500.00 union all

select  '002',200.00 union all

select  '002',200.00

 

/*  删除Ta表中字段 code,num 重复记录，保留ID值最小的记录*/

方法一：

           select min(ID) RID ,code,num  into #a from ta group by code,num having count(*)>1

           delete from Ta where ID>(select  RID from #a where #a.code=Ta.code and #a.num=Ta.num)

 方法二：

           delete from Ta where exists(select 1 from Ta T where Ta.code=T.code and Ta.num=T.num and Ta.ID>T.ID)

 

方法三：

           with tb as(

           select  row_number() over(partition by code,num order by code,num,a ) newID,code,num from ta

           )

           delete from tb where newID>1

问题2：

有表TB 如下：

create table Tb( code varchar(10) null,num float null)

insert Tb(code,num)

select '001',100.00 union all

select '001',100.00 union all

select '002',100.00 union all

select '002',200.00 union all

select '002',100.00

go

/*  删除Tb表中所有字段 存在重复记录 */

方法一：  连同重复的记录也一并删除了。

          select  code,num, count(*) as nid  into #a from Ta group by code,num having count(*)>1

          delete from Tb where exists(select 1 from #a where #a.code=code and #a.num=num)

方法二：  连同重复的记录也一并删除了。

          with ch as(

           select code,num from tb group by code,num having count(*)>1

           )

           delete  from tb where  not exists(select 1 from ch where ch.code=tb.code and ch.num=tb.num)

/*  删除Tb表中所有字段 重复记录 ,保留一条记录*/     

方法一：

           select distinct *  into #a from tb

           drop table tb

           select * into tb from #a

           drop table #a

 

方法二：

          with ch as(

           select row_number() over(partition by code,num order by code,num  ) newID,* from tb

           )

           delete from ch where m>1