字符串连接函数的BUG?怎么按时间先后累加呀.

create table tb

(

	id int,

	[name] varchar(100),

	created datetime

)

insert tb

select 1, 'a', '2010-01-01' union all

select 1, 'a', '2010-01-02' union all

select 3, 'c', '2010-01-03'



--function

alter function [dbo].[f_str](@a varchar(20),@b varchar(20))

returns varchar(50)

as

begin

  declare @s varchar(800)

  set @s = ''

  select @s = @s + '_' + ltrim(convert(varchar(10), created, 120))

  from tb

  where id=@a and [name]=@b order by  created desc

  

  if @s > ''

	set @s = right(@s, len(@s)-1)

  return @s

end



--Result

select result = dbo.[f_str] (1, 'a')

/*

result

2010-01-02_2010-01-01

*/

--你的函数中：

select @s=isnull(@s+'_','')+ltrim(c)

  from tb

--累计应该是类似这样：

select @s=@s+isnull(@s+'_','')+ltrim(c)

  from tb

create table tb(id int,name nvarchar(10),created datetime)

insert into tb select 1,'a','2010-01-01'

insert into tb select 2,'b','2010-01-02'

insert into tb select 3,'c','2010-01-03'

go

declare @s nvarchar(500)

set @s=''

select @s=@s+name from tb order by created

select @s

go

drop table tb

/*

---------------------------------------------------------------------------------------

abc



(1 行受影响)



*/

declare @table table (id int,name varchar(1),created datetime)

insert into @table

select 1,'a','2010-01-01' union all

select 2,'b','2010-01-02' union all

select 3,'c','2010-01-03'



declare @s varchar(20)

set @s=''

select @s=@s+isnull('_'+name,'') from @table order by created desc

set @s=substring(@s,2,len(@s))

select @s

/*

c_b_a

*/

  --这样就是累加了

  declare @s varchar(800)

  set @s=''

  select @s=@s+isnull(@s+'_','')+ltrim(c)

  from tb

  where a=@a and b=@b order by  tb.created desc

  return @s

select @s=isnull(@s+'_','')+ltrim(c)

from tb

where a=@a and b=@b