createfunction f_child(@pidint) returns@retable(id int,l int) as begin declare@lint set@l=0 insert@reselect id,@lfrom category where parentid=@pid while@@rowcount>0 begin set@l=@l+1 insert@reselect a.id,@l from category a join@re b on a.parentid=b.id where b.l=@l-1 end return end