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