create table tree (
  id int primary key
  , parent int null
  , foreign key FK_tree(parent) references tree(id) -- on delete cascade
  );
insert tree (id,parent) values
    (1,null),(2,1),(3,2),(4,3),(5,2),(6,5),(7,5)
  , (8,5),(9,8),(10,8),(11,8),(12,5),(13,2)
  ,(14,1),(15,14),(16,14),(17,16),(18,16),(19,16)
  ,(20,1),(21,1),(22,21),(23,22)
  ,(240,23),(25,240),(26,240);

create procedure sp_treeview (p_id int)
begin
  declare v_lvl int;
  declare v_max int;
  set v_lvl=1;
  select left('100000000',1+length(max(id))) into v_max from tree;
  
  create temporary table proc_tree select * from temp_tree where 1=0;

  delete from temp_tree;
  insert temp_tree
    select v_lvl, t.id, t.parent, insert(v_max+t.id,1,1,'')
    from tree t
    where t.id=p_id;
  while row_count()>0 do
    delete from proc_tree;
    insert proc_tree
      select v_lvl+1, t.id, t.parent, concat(v.path,'.',insert(v_max+t.id,1,1,'')) 
      from temp_tree v 
      join tree t on t.parent = v.rid
      where v.lvl=v_lvl;
    set v_lvl=v_lvl+1;
    insert temp_tree select * from proc_tree;
  end while;
  drop temporary table proc_tree;
end

create procedure sp_tree(p_id int)
begin
  create temporary table temp_tree (
      lvl int, rid int, pid int, path varchar(2000)
    , unique(rid,pid));
  call sp_treeview (p_id);
  
  -- select * from temp_tree order by path;
  delete from t_tree; insert t_tree select * from temp_tree;
  
  drop temporary table temp_tree;
end;

create table t_tree (
    lvl int, rid int, pid int, path varchar(2000)
  , unique(rid,pid));
call sp_tree(21);
select * from t_tree order by path;