请教重复数据行列互换问题

[qingniao8]

RT

-------------
TABLE

ID DATETIME CODE
1 2012-7-7 A
1 2012-7-7 B
1 2012-7-17 C
1 2012-7-24 D
2 2012-7-11 A
2 2012-7-11 B
3 2012-7-16 A
3 2012-7-16 B
3 2012-7-17 C
3 2012-7-23 D
----------------------
如何实现如下查询结果？3Q
ID A B C D
1 2012-7-7 2012-7-7 2012-7-17 2012-7-24
2 2012-7-11 2012-7-11 NULL NULL
3 2012-7-16 2012-7-16 2012-7-17 2012-7-23

[以学习为目的]

create table tb(ID int, DATETIME datetime ,code varchar(2))  
insert into tb values('1','2012-7-7','A')  
insert into tb values('1','2012-7-7','B')  
insert into tb values('1','2012-7-17','C')  
insert into tb values('1','2012-7-24','D' )  
go  
  
select ID, CODE,[DATETIME]=stuff((select ','+[DATETIME] from tb  where ID=tb.ID for xml path('')), 1, 1, '')  
from tb  
group by ID 
  
/*  
ID    A     B       C          D
  
----------- --------------------  
1  2012-7-7 2012-7-7 2012-7-17 2012-7-24

[以学习为目的]

上面是在SQL Server 2005中使用
SQL　Server 2000要创建合并函数，给你一个例子

--1. 创建处理函数 
create table tb(id int, value varchar(10))  
insert into tb values(1, 'aa')  
insert into tb values(1, 'bb')  
insert into tb values(2, 'aaa')  
insert into tb values(2, 'bbb')  
insert into tb values(2, 'ccc')  
go  
  
create function dbo.f_str(@id int)  
returns varchar(8000)  
as  
begin  
     declare @r varchar(8000)  
     set @r = ''  
     select @r = @r + ',' + value from tb where id=@id  
     return stuff(@r, 1, 1, '')  
end  
go  
  
-- 调用函数 
SELECt id, value = dbo.f_str(id) FROM tb GROUP BY id  
  
drop table tb  
drop function dbo.f_str  
  
/*  
id          value       
----------- -----------  
1          aa,bb  
2          aaa,bbb,ccc  
（所影响的行数为2 行） 
*/  

[--小F--]

http://topic.csdn.net/u/20080612/22/c850499f-bce3-4877-82d5-af2357857872.html

[百年树人]

if object_id('[tb]') is not null drop table [tb]
go
create table [tb]([ID] int,[DATETIME] datetime,[CODE] varchar(1))
insert [tb]
select 1,'2012-7-7','A' union all
select 1,'2012-7-7','B' union all
select 1,'2012-7-17','C' union all
select 1,'2012-7-24','D' union all
select 2,'2012-7-11','A' union all
select 2,'2012-7-11','B' union all
select 3,'2012-7-16','A' union all
select 3,'2012-7-16','B' union all
select 3,'2012-7-17','C' union all
select 3,'2012-7-23','D'
go

declare @sql varchar(8000)
select @sql=isnull(@sql+',','')
  +'max(case when code='''+code+''' then convert(varchar(10),datetime,120) end) as ['+code+']'
from
(select distinct code from tb) t

exec('select id,'+@sql+' from tb group by id')

/**
id          A          B          C          D
----------- ---------- ---------- ---------- ----------
1           2012-07-07 2012-07-07 2012-07-17 2012-07-24
2           2012-07-11 2012-07-11 NULL       NULL
3           2012-07-16 2012-07-16 2012-07-17 2012-07-23

(3 行受影响)

**/

[qingniao8]

5楼的方法比较易懂，1楼的好像不行。。。

[liulonglong789]

select ID,[a],[b],[c],[d]
from tb
pivot(max([datetime]) for code in ([A],[B],[C],[D])) as pvt

[youxue27]

--Score表
Name Subject Result
張三 數學 80
張三 語文 90
李四 數學 85
李四 語文 60

select name,語文=sum(case when subject='語文' then result end),數學=sum(case when subject='數學' then result end) from score group by name)


--查詢結果
姓名 語文 數學
張三 80 90
李四 85 60