if not object_id('tempdb..#t') is null
drop table #t
gocreate 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, 但無主鍵（例如沒有id...), 保留資料物理儲存最近一條
;with t as
(select rn = row_number()over(partition by [name ] order by getdate()), *
from #t
)delete t
where rn>1
或者;with t as
(select rn = row_number()over(partition by [name ] order by （select 1）), *
from #t
)delete t
where rn>1
--ii、name相同id最小的記錄(推薦用1,2,3),保留最小一條
方法1:
delete a from #t a where exists(select 1 from #t where name=a.name and id0
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
生成結果:
/*id name memo
----------- ---- ----
1 a a1
4 b b1
(2 行受影響)
*/--iii、name相同id保留最大的一條記錄:
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 max(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 max(id) from #t where name=a.name)
方法4(注:id為唯一時可用):
delete a from #t a where id not in(select max(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 desc)
方法7:
delete a from #t a where idselect * from #t
/*id name memo
----------- ---- ----
3 a a3
5 b b2
(2 行受影響)
*/
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