分組字符合並SQL語句

    /*

    標題：按某字段合併字符串之一(簡單合併)


    描述：將如下形式的數據按id字段合併value字段。
    id    value
    ----- ------
    1     aa
    1     bb
    2     aaa
    2     bbb
    2     ccc
    需要得到結果：
    id     value
    ------ -----------
    1      aa,bb
    2      aaa,bbb,ccc
    即：group by id, 求 value 的和（字符串相加）

    */


    --
    1、sql2000中只能用自定義的函數解決


    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



    --調用函數


    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、使用遊標合併數據


    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))

    --定義結果集表變量
    --定義遊標並進行合併處理

    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