SQL 行变列（学生成绩问题）

http://www.cnblogs.com/jiajinyi/archive/2009/02/18/1393239.html

SQL 行变列（学生成绩问题） 

CREATE TABLE [Test] (

[id] [int] IDENTITY (1, 1) NOT NULL ,

[name] [nvarchar] (50) COLLATE Chinese_PRC_CI_AS NULL ,

[subject] [nvarchar] (50) COLLATE Chinese_PRC_CI_AS NULL ,

[Source] [numeric](18, 0) NULL 

) ON [PRIMARY]

GO

INSERT INTO [test] ([name],[subject],[Source]) values (N'张三',N'语文',60)

INSERT INTO [test] ([name],[subject],[Source]) values (N'李四',N'数学',70)

INSERT INTO [test] ([name],[subject],[Source]) values (N'王五',N'英语',80)

INSERT INTO [test] ([name],[subject],[Source]) values (N'王五',N'数学',75)

INSERT INTO [test] ([name],[subject],[Source]) values (N'王五',N'语文',57)

INSERT INTO [test] ([name],[subject],[Source]) values (N'李四',N'语文',80)

INSERT INTO [test] ([name],[subject],[Source]) values (N'张三',N'英语',100)

Go

--交叉表语句的实现：

--用于：交叉表的列数是确定的

select name,sum(case subject when '数学' then source else 0 end) as '数学',

sum(case subject when '英语' then source else 0 end) as '英语',

sum(case subject when '语文' then source else 0 end) as '语文'

from test 

group by name

--用于：交叉表的列数是不确定的

declare @sql varchar(8000)

set @sql = 'select name,'

select @sql = @sql + 'sum(case subject when '''+subject+''' 

then source else 0 end) as '''+subject+''','

from (select distinct subject from test) as a 

select @sql

select @sql = left(@sql,len(@sql)-1) + ' from test group by name'

select @sql

exec(@sql)

go

--显示共有多少科目 

declare @subCount nvarchar(200)

set @subCount = '' --必须,否则print没有内容

select @subCount = @subCount + ',' + subject from test

set @subCount = substring(@stus,2,len(@stus)-1)

print @subCount --语文,数学,英语 select @stus

go