假设有一下表：
字段1 字段2
a b1
a b2
a b3
c d1
c d2
也就是说存在一对多的关系，怎么用SQL语句把他变成杭的关系，比如变成：
字段1 字段21 字段22 字段23 字段24 字段25
a b1 b2 b3 0 0
c d1 d2 0 0 0
--------------------------------------------------------------------------------------------
1: 列转为行:
eg1:
Create table test (name char(10),km char(10),cj int)
go
insert test values('张三','语文',80)
insert test values('张三','数学',86)
insert test values('张三','英语',75)
insert test values('李四','语文',78)
insert test values('李四','数学',85)
insert test values('李四','英语',78)
想变成
姓名 语文 数学 英语
张三 80 86 75
李四 78 85 78
declare @sql varchar(8000)
set @sql = 'select name'
select @sql = @sql + ',sum(case km when'''+km+''' then cj end) ['+km+']' from (select distinct km from test) as a
select @sql = @sql+' from test group by name'
exec(@sql)
drop table test
eg2:
有表A,
id pid
1 1
1 2
1 3
2 1
2 2
3 1
如何化成表B:
id pid
1 1,2,3
2 1,2
3 1
或者是从表B变成A(不要用游标)
--1.创建一个合并的函数
create function fmerg(@id int)
returns varchar(8000)
as
begin
declare @str varchar(8000)
set @str=''
select @str=@str+','+cast(pid as varchar) from 表A where
set @str=right(@str,len(@str)-1)
return(@str)
End
go
--调用自定义函数得到结果
select distinct id,dbo.fmerg(id) from 表A
--==================
2:
/*********** 行转列 *****************/
测试：
create table t1 (a int,b int,c int,d int,e int,f int,g int,h int)
insert t1 values(15, 9, 1, 0, 1, 2, 2, 0)
declare @ varchar(8000)
set @=''
select @=@+rtrim(name)+'from t1 union all select'from syscolumns where
t1')
set @=left(@,len(@)-len(' from t1 union all select '))
--print @
exec('select '+@+' from t1')
a
-----------
15
9
1
0
1
2
2
0
3:
将结果矩阵转置
if exists (select*from sysobjects where proc_sky_blue') and xtype ='P')
drop proc proc_sky_blue
go
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('表的行数太多了，我转不了',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 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
go
----------------分析
declare @tablename varchar(200)
set @tablename='table1'
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('表的行数太多了，我转不了',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 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) +')'
select @insertsql
--exec(@insertsql)
fetch next from my_cursor into @col
end
close my_cursor
deallocate my_cursor
select * from #tmp
set nocount off
drop table #tmp
end
end
-------------------------------------------------------------------------------------------------------------------------------------
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
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