矩陣轉置
有表 unknown
nam a c b d
--------------------------------------
Tom 1 2 3 4
Sun 5 6 7 8
mon 9 10 11 12
das 13 14 15 16
hor 17 18 19 20
要求以縱向格式顯示
name col1 col2 col3 col4 col5
----------------------------------------------
nam tom sun mon das hor
a 1 5 9 13 17
c 2 6 10 14 18
b 3 7 11 15 19
d 4 8 12 16 20
方法一：使用循環。
create table test(nam varchar(4),a int,c int,b int,d int)
insert test(nam,a,c,b,d)
select 'Tom', 1, 2, 3, 4
union all select 'Sun' , 5 , 6 , 7 , 8
union all select 'mon' , 9 , 10 , 11, 12
union all select 'das' , 13 , 14 , 15, 16
union all select 'hor' , 17 , 18 , 19 , 20
create proc proc_sky_blue (@tablename varchar(200))
as
begin
set nocount on
declare @col nvarchar(256)
declare @makesql nvarchar(4000)
declare @insertsql nvarchar(4000)
declare @caculatesql nvarchar(400)
declare @count int
declare @i int
create table #tmp (colname nvarchar(20))
select @caculatesql = 'select @count=count(1) from ' + @tablename
exec sp_executesql @caculatesql, N'@count int output',@count output
if @count >=1024
begin
raiserror('表的行數太多了，我轉不了',16,1)
end
else
begin
select @i=0
while @count >0
begin
select @i=@i+1
select @makesql = 'alter table #tmp add col'+convert(varchar(20),@i)+' int'
exec(@makesql)
select @count=@count-1
end
declare my_cursor cursor for
select name from syscolumns where id=object_id(@tablename) order by colid
open my_cursor
fetch next from my_cursor into @col
while @@fetch_status = 0
begin
select @makesql ='select @insertsql= @insertsql + convert(varchar(4),'+@col+') +'','' from ' +@tablename
select @insertsql =N'insert #tmp values ('''+@col+ ''','
execute sp_executesql @makesql,N'@insertsql nvarchar(4000) output' ,@insertsql output
select @insertsql = left(@insertsql,len(@insertsql)-1) +')'
exec(@insertsql)
fetch next from my_cursor into @col
end
close my_cursor
deallocate my_cursor
select * from #tmp
set nocount off
end
end
exec proc_sky_blue 'test'
drop table test
drop proc proc_sky_blue
方法二：
--測試數據
create table test(nam varchar(4),a int,c int,b int,d int)
insert test(nam,a,c,b,d)
select 'Tom', 1, 2, 3, 4
union all select 'Sun' , 5 , 6 , 7 , 8
union all select 'mon' , 9 , 10 , 11, 12
union all select 'das' , 13 , 14 , 15, 16
union all select 'hor' , 17 , 18 , 19 , 20
union all select 'Jun' , 9 , 10 , 11, 12
union all select 'Feb' , 13 , 14 , 15, 16
union all select 'Mar' , 17 , 18 , 19 , 20
union all select 'Apr' , 9 , 10 , 11, 12
union all select 'May' , 13 , 14 , 15, 16
union all select 'Jun' , 17 , 18 , 19 , 20
union all select 'Jul' , 9 , 10 , 11, 12
union all select 'Aug' , 13 , 14 , 15, 16
union all select 'Sep' , 17 , 18 , 19 , 20
union all select 'Oct' , 9 , 10 , 11, 12
union all select 'Nov' , 13 , 14 , 15, 16
union all select 'Dec' , 17 , 18 , 19 , 20
--查詢處理
declare @s1 varchar(8000),@s2 varchar(8000)
,@s3 varchar(8000),@s4 varchar(8000),@s5 varchar(8000)
,@i varchar(10)
select @s1='',@s2='',@s3='',@s4='',@s5='',@i='0'
select @s1=@s1+',@'+@i+' varchar(800)'
,@s2=@s2+',@'+@i+'='''''
,@s3=@s3+'
select @'+@i+'=@'+@i+'+'',[''+nam+'']=''+cast(['+name+'] as varchar) from test'
,@s4=@s4+',@'+@i+'=''select ''+substring(@'+@i+',2,8000)'
,@s5=@s5+'+'' union all ''+@'+@i
,@i=cast(@i as int)+1
from syscolumns
where object_id('test')=id and colid<>1
select @s1=substring(@s1,2,8000)
,@s2=substring(@s2,2,8000)
,@s4=substring(@s4,2,8000)
,@s5=substring(@s5,16,8000)
select @s1,@s2,@s3,@s4,@s5
exec('declare '+@s1+'
select '+@s2+@s3+'
select '+@s4+'
exec('+@s5+')')
go
--刪除測試表
drop table test
解讀：N列數據用N-1個變量來保存N-1列的數據列表，其中第一列作爲字段。
此方法靈活地應用了動態語句的特點，其大致思路是一次取得一列數據的值。
即展開後s3的值爲：
select @0=@0+',['+nam+']='+cast([a] as varchar) from test
select @1=@1+',['+nam+']='+cast([c] as varchar) from test
select @2=@2+',['+nam+']='+cast([b] as varchar) from test
select @3=@3+',['+nam+']='+cast([d] as varchar) from test
缺點：受被轉換的數據行行數限制，即上面的@0,@1,@2,@3最大隻能容納8000個字符
轉換後的行不能超過1024行，這是數據庫的限制。
本文來自CSDN博客，轉載請標明出處：http://blog.csdn.net/lee576/archive/2006/12/11/1438973.aspx