if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[TB_Student]') and OBJECTPROPERTY(id, N'IsUserTable') = 1)
drop table [dbo].[TB_Student]
GOCREATE TABLE [dbo].[TB_Student] (
[strStudent] [nvarchar] (50) COLLATE Chinese_PRC_CI_AS NOT NULL ,
[strClass] [nvarchar] (50) COLLATE Chinese_PRC_CI_AS NOT NULL ,
[nScore] [int] NOT NULL
) ON [PRIMARY]
GOinsert into TB_Student(strStudent,strClass,nScore) values('张三','语文',65)
insert into TB_Student(strStudent,strClass,nScore) values('张三','数学',85)
insert into TB_Student(strStudent,strClass,nScore) values('张三','英语',90)
insert into TB_Student(strStudent,strClass,nScore) values('李四','语文',56)
insert into TB_Student(strStudent,strClass,nScore) values('李四','数学',67)
insert into TB_Student(strStudent,strClass,nScore) values('李四','英语',89)
insert into TB_Student(strStudent,strClass,nScore) values('王五','语文',56)
insert into TB_Student(strStudent,strClass,nScore) values('王五','数学',55)
insert into TB_Student(strStudent,strClass,nScore) values('王五','英语',87)/*
结果 姓名 学科 成绩
'张三','英语',90
'李四','英语',89
'王五','英语',87
*/--谢谢 各位
where not exists(select 1 from TB_Student where strStudent=t.strStudent and nScore>t.nScore)
为什么不直接用select * from dbo.TB_Student where strclass='英语'
select * from TB_Student a
where nScore=(select max(nScore) from TB_Student where strStudent=a.strStudent)
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),方法3在SQl05时,效率高于1、2
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)--SQL2005: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)
*/
--II、Name相同ID最大的记录,与min相反:
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)--SQL2005: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)
*/