表结构是这样的
表名score
字段名:
scoreid course studentid score
1 数学 2 98
2 数学 3 97
3 数学 4 96
4 语文 3 30
5 语文 1 31
想得到每门课score分数最高的studentid我的写法是这样的,
select b.studentid from (select max(score) t,course from score group by course) a,score b where a.t=b.score and a.course=b.course
结果可以得到,并且是正确的,但总觉得有点不好,大家通常如何写一条sql解决这个问题?
表名score
字段名:
scoreid course studentid score
1 数学 2 98
2 数学 3 97
3 数学 4 96
4 语文 3 30
5 语文 1 31
想得到每门课score分数最高的studentid我的写法是这样的,
select b.studentid from (select max(score) t,course from score group by course) a,score b where a.t=b.score and a.course=b.course
结果可以得到,并且是正确的,但总觉得有点不好,大家通常如何写一条sql解决这个问题?
declare @score table
(scoreid int,course varchar(4),studentid int,score int)
insert into @score
select 1,'数学',2,98 union all
select 2,'数学',3,97 union all
select 3,'数学',4,96 union all
select 4,'语文',3,30 union all
select 5,'语文',1,31select * from @score a
where score=(select max(score) from @score where course=a.course)
/*
scoreid course studentid score
----------- ------ ----------- -----------
5 语文 1 31
1 数学 2 98
*/
/******************************************************************************************************************************************************
Name相同ID最小或最大的记录整理人:中国风(Roy)日期:2008.06.06
******************************************************************************************************************************************************/--> --> (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
--1、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:
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
生成结果:
/*
ID Name Memo
----------- ---- ----
1 A A1
4 B B1(2 行受影响)
*/
--2、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:
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生成结果2:
/*
ID Name Memo
----------- ---- ----
3 A A3
5 B B2(2 行受影响)
*/
where not exists(select 1 from t1 where a.course=course and a.score<score)