/******************************************************************************************************************************************************
1、Num、Name相同的重复值记录,没有大小关系只保留一条
2、Name相同,ID有大小关系时,保留大或小其中一个记录
******************************************************************************************************************************************************/
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
方法1:
Select * from #T a where not exists(select 1 from #T where Name=a.Name and ID<a.ID)
方法2:
select a.* from #T a join (select min(ID)ID,Name from #T group by Name) b on a.Name=b.Name and a.ID=b.ID
方法3:
select * from #T a where ID=(select min(ID) from #T where Name=a.Name)
方法4:
select a.* from #T a join #T b on a.Name=b.Name and a.ID>=b.ID group by a.ID,a.Name,a.Memo having count(1)=1
方法5:
select * from #T a group by ID,Name,Memo having ID=(select min(ID)from #T where Name=a.Name)
方法6:
select * from #T a where (select count(1) from #T where Name=a.Name and ID<a.ID)=0
方法7:
select * from #T a where ID=(select top 1 ID from #T where Name=a.name order by ID)
方法8:
select * from #T a where ID!>all(select ID from #T where Name=a.Name)
方法9(注:ID为唯一时可用):
select * from #T a where ID in(select min(ID) from #T group by Name)
方法10:
select ID,Name,Memo from (select *,min(ID)over(partition by Name) as MinID from #T a)T where ID=MinID
方法11:
select ID,Name,Memo from (select *,row_number()over(partition by Name order by ID) as MinID from #T a)T where MinID=1
生成结果:
/*
ID Name Memo
1 A A1
4 B B1
(2 行受影响)
*/
方法1:
Select * from #T a where not exists(select 1 from #T where Name=a.Name and ID>a.ID)
方法2:
select a.* from #T a join (select max(ID)ID,Name from #T group by Name) b on a.Name=b.Name and a.ID=b.ID order by ID
方法3:
select * from #T a where ID=(select max(ID) from #T where Name=a.Name) order by ID
方法4:
select a.* from #T a join #T b on a.Name=b.Name and a.ID<=b.ID group by a.ID,a.Name,a.Memo having count(1)=1
方法5:
select * from #T a group by ID,Name,Memo having ID=(select max(ID)from #T where Name=a.Name)
方法6:
select * from #T a where (select count(1) from #T where Name=a.Name and ID>a.ID)=0
方法7:
select * from #T a where ID=(select top 1 ID from #T where Name=a.name order by ID desc)
方法8:
select * from #T a where ID!<all(select ID from #T where Name=a.Name)
方法9(注:ID为唯一时可用):
select * from #T a where ID in(select max(ID) from #T group by Name)
方法10:
select ID,Name,Memo from (select *,max(ID)over(partition by Name) as MinID from #T a)T where ID=MinID
方法11:
select ID,Name,Memo from (select *,row_number()over(partition by Name order by ID desc) as MinID from #T a)T where MinID=1
生成结果2:
/*
ID Name Memo
3 A A3
5 B B2
(2 行受影响)
*/
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
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)
*/
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)
*/
if not object_id(\'Tempdb..#T\') is null
drop table #T
Go
Create table #T([Num] int,[Name] nvarchar(1))
Insert #T
select 1,N\'A\' union all
select 1,N\'A\' union all
select 1,N\'A\' union all
select 2,N\'B\' union all
select 2,N\'B\'
Go
方法1:
if object_id(\'Tempdb..#\') is not null
drop table #
Select distinct * into # from #T
truncate table #T
insert #T select * from #
select * from #T
/*
Num Name
1 A
2 B
(2 行受影响)
*/
方法2:
alter table #T add ID int identity
go
delete a from #T a where exists(select 1 from #T where Num=a.Num and Name=a.Name and ID>a.ID)
go
alter table #T drop column ID
select * from #T
/*
Num Name
1 A
2 B
(2 行受影响)
*/
方法3:
declare Roy_Cursor cursor local for
select count(1)-1,Num,Name from #T group by Num,Name having count(1)>1
declare @con int,@Num int,@Name nvarchar(1)
open Roy_Cursor
fetch next from Roy_Cursor into @con,@Num,@Name
while @@Fetch_status=0
begin
set rowcount @con;
delete #T where Num=@Num and Name=@Name
set rowcount 0;
fetch next from Roy_Cursor into @con,@Num,@Name
end
close Roy_Cursor
deallocate Roy_Cursor
select * from #T
/*
Num Name
1 A
2 B
(2 行受影响)
*/