为什么 @all 结果却是空的？？？？

[gegangqiao]

declare @orderno char(11)
declare @all char(8000)
declare @da char(8000)
select @da=''
select @all='aaa'

declare dd cursor for select orderno from fastorder
open dd
fetch next from dd into @orderno

while @@fetch_status<>-1
begin
select @all=@da+@orderno --orderno 的定义: orderno char(11)
select @da=@all
fetch next from dd into @orderno
end

close dd
deallocate dd

select @all

[wei9625]

orderno 有没有可能出现NULL值

[gegangqiao]

没有，我改过来之后还是一样。
select @all=@all+case when @orderno=null then ' ' else @orderno end
@all 还是空的

[CrazyFor]

declare @orderno varchar(11)
declare @all varchar(8000)
declare @da varchar(8000)
select @da=''
select @all='aaa'
..................

[CrazyFor]

declare @orderno varchar(11)
declare @all varchar(8000)
declare @da varchar(8000)
select @da=''
select @all='aaa'
..................

[77zjh77]

select @all=@all+ case when @orderno=null then ' ' else @orderno end

修改成

select @all=@all+case when isnull(@orderno,'')='' then ' ' else @orderno end

[gegangqiao]

以上均未能解决问题，为了方便，我改了一下，只要打开PUBS库就可以直接COPY进去测试。


declare @orderno char(20)
declare @all char(8000)
set @all='aa'

declare dd cursor for select au_lname from authors
open dd
fetch next from dd into @orderno

while @@fetch_status<>-1
begin

select @all=@all+case when isnull(@orderno,'')='' then ' ' else @orderno end

--select @all=@all+@orderno --orderno 的定义: orderno char(11)
fetch next from dd into @orderno
end

select @all 'all orderno'

close dd
deallocate dd

[gmlxf]

declare @orderno varchar(11)
declare @all varchar(8000)
declare @da varchar(8000)