学步园

/*

标题：按某字段合并字符串之一(简单合并)


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