SQL Server 2005开始，我们可以直接通过CTE来支持递归查询,CTE即公用表表达式

 百度百科 公用表表达式（CTE），是一个在查询中定义的临时命名结果集将在from子句中使用它。每个CTE仅被定义一次（但在其作用域内可以被引用任意次），并且在该查询生存期间将一直生存。可以使用CTE来执行递归操作。创建的语法是：with <name of you cte>(<column names>)as(<actual query>)select * from <name of your cte> 生成数据 --菜单目录结构表create table tb_menu( id int not null, --主键idtitle 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; 2.查找所有上级节点 --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;  3.查找下级节点带level  --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;