SQL去除重复记录（七种）

话不多说，请看代码：

if not object_id('tempdb..#t') is null
 drop table #t
go
create table #t([id] int,[name] nvarchar(1),[memo] nvarchar(2))
insert #t
select 1,n'a',n'a1' union all
select 2,n'a',n'a2' union all
select 3,n'a',n'a3' union all
select 4,n'b',n'b1' union all
select 5,n'b',n'b2'
go 

--i、name相同id最小的记录(推荐用1,2,3),保留最小一条

方法1:

delete a from #t a where  exists(select 1 from #t where name=a.name and id<a.id)

方法2:

delete a from #t a left join (select min(id)id,name from #t group by name) b on a.name=b.name and a.id=b.id where b.id is null

方法3:

delete a from #t a where id not in (select min(id) from #t where name=a.name)

方法4(注:id为唯一时可用):

delete a from #t a where id not in(select min(id)from #t group by name)

方法5:

delete a from #t a where (select count(1) from #t where name=a.name and id<a.id)>0

方法6:

delete a from #t a where id<>(select top 1 id from #t where name=a.name order by id)

方法7:

delete a from #t a where id>any(select id from #t where name=a.name)
select * from #t

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