--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;