[sql server] 合并字符串

本文转载：http://blog.csdn.net/leamonjxl/article/details/7042317

 

很实用的帖子，收藏学习。。。。。。。
 /*标题：按某字段合并字符串之一(简单合并)
 

作者：爱新觉罗.毓华(十八年风雨,守得冰山雪莲花开)
 时间：2008-11-06
 地点：广东深圳
 
描述：将如下形式的数据按id字段合并value字段。
 id    value
 ----- ------
 1     aa
 1     bb
 2     aaa
 2     bbb
 2     ccc
 需要得到结果：
 id     value
 ------ -----------
 1      aa,bb
 2      aaa,bbb,ccc
 即：group by id, 求 value 的和（字符串相加）
 */
 --1、sql2000中只能用自定义的函数解决
 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(100)
 as
 begin
     declare @str varchar(1000)
     set @str = ''
     select @str = @str + ',' + cast(value as varchar) from tb where id = @id
     set @str = right(@str , len(@str) - 1)
     return @str
 end
 go
 
--调用函数
 select id , value = dbo.f_str(id) from tb group by id
 
drop function dbo.f_str
 drop table tb
 

--2、sql2005中的方法
 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
 
select id, [value] = stuff((select ',' + [value] from tb t where id = tb.id for xml path('')) , 1 , 1 , '')
 from tb
 group by id
 
drop table tb
 

--3、使用游标合并数据
 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
 declare @t table(id int,value varchar(100))--定义结果集表变量
 --定义游标并进行合并处理
 declare my_cursor cursor local for
 select id , value from tb
 declare @id_old int , @id int , @value varchar(10) , @s varchar(100)
 open my_cursor
 fetch my_cursor into @id , @value
 select @id_old = @id , @s=''
 while @@FETCH_STATUS = 0
 begin
     if @id = @id_old
        select @s = @s + ',' + cast(@value as varchar)
     else
       begin
         insert @t values(@id_old , stuff(@s,1,1,''))
         select @s = ',' + cast(@value as varchar) , @id_old = @id
       end
     fetch my_cursor into @id , @value
 END
 insert @t values(@id_old , stuff(@s,1,1,''))
 close my_cursor
 deallocate my_cursor
 
select * from @t
 drop table tb