如果你不想递归，请使用FullPathID，如果对你有用，请鼓鼓掌

--1 create table
drop table FullPathTable
go
create table FullPathTable(
PathID integer identity,
PathName varchar(50),
ParentID integer,
InternalOrder integer,
FullPathID varchar(50))

--2 create trigger to FullPathTable

create trigger tr_FullPath
   on  FullPathTable
   after insert
as
begin

 declare @internalOrder integer, @str1 varchar(10), @parentFullPathID varchar(100),@FullPathID varchar(100)
  ,@parentID integer, @PathID integer
 select @PathID = @@identity
 select @parentID = ParentID from inserted
 
if(@parentID = -1
 or (@parentID <> -1 and exists(select * from FullPathTable where PathID = @parentID and @parentID != @PathID))
 )
 begin
  select @parentFullPathID = FullPathID from FullPathTable where PathID = @parentID
  select @internalOrder = isnull(max(InternalOrder),0) from FullPathTable where ParentID = @parentID
  set @internalOrder = @internalOrder + 1
  set @str1 = '00000'

  set @FullPathID = substring(@str1,1,len(@str1)-len(Convert(varchar,@internalOrder))) + Convert(varchar,@internalOrder)

  if(@parentFullPathID <> '')
    set @FullPathID = @parentFullPathID + '|' + @FullPathID
   
  update FullPathTable
  set FullPathID = @FullPathID, InternalOrder = @internalOrder
  where PathID = @PathID
  
 end
end

--3 insert data
insert into FullPathTable(PathName,ParentID) values('第3级1',5)

--4 query data
select * from FullPathTable
1 第一级1 -1 1 00001
2 第一级2 -1 2 00002
3 第一级3 -1 3 00003
4 第2级1 2 1 00002|00001
5 第2级2 2 2 00002|00002
6 第3级1 5 1 00002|00002|00001

select * from FullPathTable where FullPathID like '00002|%'
4 第2级1 2 1 00002|00001
5 第2级2 2 2 00002|00002
6 第3级1 5 1 00002|00002|00001

--5 主要作用，减少循环递归，用于多级数据结构，层次深度不定的情况