SQL 自定义函数获得树型结构下的所有子孙节点

create function ufGetChildCategoryIDs(@id int)
returns varchar(8000)
as
begin
declare @t table(id int,parentid int,lev int)
declare @lev int
set @lev=1
insert into @t select CategoryID,Parent, @lev from tblCategory where CategoryID=@id
while(@@rowcount>0)
begin
set @lev=@lev+1
insert into @t select a.CategoryID,Parent, @lev from tblCategory a,@t b
where a.parent=b.id and b.lev=@lev-1
end
declare @cids varchar(8000)
select @cids=isnull(@cids+',','')+ltrim(id) from @t order by lev
return @cids
end
go