DELETE T FROM TB T WHERE EXISTS(SELECT 1 FROM TB WHERE A=T.A AND B=T.B AND C=T.C AND TIME<T.TIME)
删除重复记录有大小关系时,保留大或小其中一个记录 --> --> (Roy)生成測試數據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生成结果: /* ID Name Memo ----------- ---- ---- 1 A A1 4 B B1(2 行受影响) */ --II、Name相同ID保留最大的一条记录: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为唯一时可用): 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 ID<any(select ID from #T where Name=a.Name) select * from #T /* ID Name Memo ----------- ---- ---- 3 A A3 5 B B2(2 行受影响) */
同意楼上的,去最小的ID ,用min
delete tb from tb t where dt not in (select dt from tb where c1 = t.c1 and c2 = t.c2 and c3 = t.c3)
select * from tableName t where uid =(select min(uid) from tableName where uid=t.uid)
WHERE EXISTS(SELECT 1 FROM TB WHERE A=T.A AND B=T.B AND C=T.C AND TIME<T.TIME)
--> --> (Roy)生成測試數據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生成结果:
/*
ID Name Memo
----------- ---- ----
1 A A1
4 B B1(2 行受影响)
*/
--II、Name相同ID保留最大的一条记录: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为唯一时可用):
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 ID<any(select ID from #T where Name=a.Name)
select * from #T
/*
ID Name Memo
----------- ---- ----
3 A A3
5 B B2(2 行受影响)
*/