with name of you cte>(column names>)
as(
actual query>
)
select * from name of your cte>

--菜单目录结构表 
create table tb_menu( 
 id int not null, --主键id 
title varchar(50), --标题 
 parent int --parent id 
); 
--父菜单 
insert into tb_menu(id, title, parent) values(1, '父菜单1',null); 
insert into tb_menu(id, title, parent) values(2, '父菜单2',null); 
insert into tb_menu(id, title, parent) values(3, '父菜单3',null); 
insert into tb_menu(id, title, parent) values(4, '父菜单4',null); 
insert into tb_menu(id, title, parent) values(5, '父菜单5',null); 
--一级菜单 
insert into tb_menu(id, title, parent) values(6, '一级菜单6',1); 
insert into tb_menu(id, title, parent) values(7, '一级菜单7',1); 
insert into tb_menu(id, title, parent) values(8, '一级菜单8',1); 
insert into tb_menu(id, title, parent) values(9, '一级菜单9',2); 
insert into tb_menu(id, title, parent) values(10, '一级菜单10',2); 
insert into tb_menu(id, title, parent) values(11, '一级菜单11',2); 
insert into tb_menu(id, title, parent) values(12, '一级菜单12',3); 
insert into tb_menu(id, title, parent) values(13, '一级菜单13',3); 
insert into tb_menu(id, title, parent) values(14, '一级菜单14',3); 
insert into tb_menu(id, title, parent) values(15, '一级菜单15',4); 
insert into tb_menu(id, title, parent) values(16, '一级菜单16',4); 
insert into tb_menu(id, title, parent) values(17, '一级菜单17',4); 
insert into tb_menu(id, title, parent) values(18, '一级菜单18',5); 
insert into tb_menu(id, title, parent) values(19, '一级菜单19',5); 
insert into tb_menu(id, title, parent) values(20, '一级菜单20',5); 
--二级菜单 
insert into tb_menu(id, title, parent) values(21, '二级菜单21',6); 
insert into tb_menu(id, title, parent) values(22, '二级菜单22',6); 
insert into tb_menu(id, title, parent) values(23, '二级菜单23',7); 
insert into tb_menu(id, title, parent) values(24, '二级菜单24',7); 
insert into tb_menu(id, title, parent) values(25, '二级菜单25',8); 
insert into tb_menu(id, title, parent) values(26, '二级菜单26',9); 
insert into tb_menu(id, title, parent) values(27, '二级菜单27',10); 
insert into tb_menu(id, title, parent) values(28, '二级菜单28',11); 
insert into tb_menu(id, title, parent) values(29, '二级菜单29',12); 
insert into tb_menu(id, title, parent) values(30, '二级菜单30',13); 
insert into tb_menu(id, title, parent) values(31, '二级菜单31',14); 
insert into tb_menu(id, title, parent) values(32, '二级菜单32',15); 
insert into tb_menu(id, title, parent) values(33, '二级菜单33',16); 
insert into tb_menu(id, title, parent) values(34, '二级菜单34',17); 
insert into tb_menu(id, title, parent) values(35, '二级菜单35',18); 
insert into tb_menu(id, title, parent) values(36, '二级菜单36',19); 
insert into tb_menu(id, title, parent) values(37, '二级菜单37',20); 
 
--三级菜单 
insert into tb_menu(id, title, parent) values(38, '三级菜单38',21); 
insert into tb_menu(id, title, parent) values(39, '三级菜单39',22); 
insert into tb_menu(id, title, parent) values(40, '三级菜单40',23); 
insert into tb_menu(id, title, parent) values(41, '三级菜单41',24); 
insert into tb_menu(id, title, parent) values(42, '三级菜单42',25); 
insert into tb_menu(id, title, parent) values(43, '三级菜单43',26); 
insert into tb_menu(id, title, parent) values(44, '三级菜单44',27); 
insert into tb_menu(id, title, parent) values(45, '三级菜单45',28); 
insert into tb_menu(id, title, parent) values(46, '三级菜单46',28); 
insert into tb_menu(id, title, parent) values(47, '三级菜单47',29); 
insert into tb_menu(id, title, parent) values(48, '三级菜单48',30); 
insert into tb_menu(id, title, parent) values(49, '三级菜单49',31); 
insert into tb_menu(id, title, parent) values(50, '三级菜单50',31); 
commit; 

--查询树状结构某节点(44)的上级所有根节点 
 
with cte_parent(id,title,parent) 
 
as 
 
( 
 
  --起始条件 
 
  select id,title,parent 
 
  from tb_menu 
 
  where id = 44  --列出子节点查询条件 
 
  union all 
 
  --递归条件 
 
  select a.id,a.title,a.parent 
 
  from tb_menu a 
 
  inner join  
 
  cte_parent b     --执行递归，这里就要理解下了  
 
  on a.id=b.parent  
 
)             
 
select * from cte_parent; 

--查询树状结构某节点下的所有子节点( 
 
with cte_child(id,title,parent,level) 
 
as 
 
( 
 
  --起始条件 
 
  select id,title,parent,0 as level 
 
  from tb_menu 
 
  where id = 6--列出父节点查询条件 
 
  union all 
 
  --递归条件 
 
  select a.id,a.title,a.parent,b.level+1 
 
  from tb_menu a 
 
  inner join  
 
  cte_child b 
 
  on ( a.parent=b.id)  
 
) 
 
select * from cte_child;