sql 实现递归算法

最近一段上csdn的时间比较多，浏览了不少sql server 版面的帖子，发现根据传入参数查找指定项的子项的递归用法提问的比较多，所以在这里总结一下：
样表：
child,parent
1 0
2 0
3 1
4 2
要实现这种用法一般都通过两种方式来实现：
procedure 方式：
create procedure usp_getallchild(@child int)
as
declare @t table(child int null,parent int null,level int null)
declare @level int
set @level=0
insert into @t(child,parent,level) select child,parent,@level from table where child=@child
while @@rowcount>0
begin
set @level=@level+1
insert into @t(child,parent,level) select child,parent,@level from table jion @t as t on t.child=table.parent where t.level=@level-1

end
select * from @t

function 方式：
create function udf_getallchild(@child int)
returns @t_return table(child int null,parent int null,level int null)
as
begin

declare @level int
set @level=0
insert into @t_return(child,parent,level) select child,parent,@level from table where child=@child
while @@rowcount>0
begin
set @level=@level+1
insert into @t(child,parent,level) select child,parent,@level from table jion @t_return as t on t.child=table.parent where t.level=@level-1

end
return @t_return
end