sql server行转列 列转行交叉表实现[转]

主要应用case语句来解决行转列的问题
行转列问题主要分为两类

1)简单的行转列问题:

示例表:

id sid           course result

1   2005001 语文     80.0
2   2005001 数学     90.0
3   2005001 英语     80.0
4   2005002 语文     56.0
5   2005002 数学     69.0
6   2005002 英语     89.0

执行

select sid,语文=isnull(sum(case course when '语文' then result end),0),
   数学=isnull(sum(case course when '数学' then result end),0),
   英语=isnull(sum(case course when '英语' then result end),0)
   from result
   group by sid
   order by sid

得出结果

sid           语文 数学 英语

2005001 80.0 90.0 80.0
2005002 56.0 69.0 89.0

2)较为复杂的行转列

表1:course

id name

1 语文
2 数学
3 英语

表2:result

id sid          course result

1 2005001 语文      80.0
2 2005001 数学      90.0
3 2005001 英语      80.0
4 2005002 语文      56.0
5 2005002 数学      69.0
6 2005002 英语      89.0

declare @sql varchar(8000)
set @sql='select sid'
select @sql=@sql+','+course.name+'=isnull(sum(case course when '''+course.name+''' then result end),0)'
from course order by id
set @sql=@sql+' from result group by sid order by sid'
print @sql
exec(@sql)

得出结果

sid           语文 数学 英语

2005001 80.0 90.0 80.0
2005002 56.0 69.0 89.0

-----------------列转行---------------------------------------------------------------------------------------------------------

有字符串'1,2,3,4,5,,6,7,8,'这样的不定长字符串,要求将其转成一列N行来存储,也就是列转行,哪种方式最快.

经过讨论,下列方式最快.

declare @var varchar(8000)
    ,@sql varchar(8000)
    ,@last varchar(1)
    ,@ctrl int
set @var='1,2,3,4,5,,6,7,'
set @ctrl=0
while @ctrl=0
begin
if (select charindex(',,',@var))>0
    select @var=replace(@var,',,',',')
else
    set @ctrl=1
end

set @last=right(@var,1)

if @last=','
set @var=left(@var,len(@var)-1)

set @sql='select '+replace(@var,',',' union all select '

 

-------------------------------------------------可运行的------------------------------------

--交叉表语句的实现：
CREATE TABLE Test
(
id int IDENTITY(1,1) NOT NULL,
name nvarchar(50) NULL,
subject nvarchar(50) NULL,
Source numeric(18,0) NULL
)

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

SELECT * FROM TEST

--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 = @sql + ' from test group by name'
exec(@sql)