找到一篇好文，真的解決了很多問題
轉載自：https://blog.csdn.net/jethai/article/details/52345361
SQL Server 2005開始，我們可以直接通過CTE來支持遞歸查詢,CTE即公用表表達式
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公用表表達式（CTE），是一個在查詢中定義的臨時命名結果集將在from子句中使用它。每個CTE僅被定義一次（但在其作用域內可以被引用任意次），並且在該查詢生存期間將一直生存。可以使用CTE來執行遞歸操作。創建的語法是：
with <name of you cte>(<column names>)
as(
<actual query>
)
select * from <name of your cte>
生成數據
--菜單目錄結構表
create table tb_menu(
id int not null, --主鍵id
title varchar(50), --標題
parent int --parent id
);
--父菜單
insert into tb_menu(id, title, parent) values(1, '父菜單1',null);
insert into tb_menu(id, title, parent) values(2, '父菜單2',null);
insert into tb_menu(id, title, parent) values(3, '父菜單3',null);
insert into tb_menu(id, title, parent) values(4, '父菜單4',null);
insert into tb_menu(id, title, parent) values(5, '父菜單5',null);
--一級菜單
insert into tb_menu(id, title, parent) values(6, '一級菜單6',1);
insert into tb_menu(id, title, parent) values(7, '一級菜單7',1);
insert into tb_menu(id, title, parent) values(8, '一級菜單8',1);
insert into tb_menu(id, title, parent) values(9, '一級菜單9',2);
insert into tb_menu(id, title, parent) values(10, '一級菜單10',2);
insert into tb_menu(id, title, parent) values(11, '一級菜單11',2);
insert into tb_menu(id, title, parent) values(12, '一級菜單12',3);
insert into tb_menu(id, title, parent) values(13, '一級菜單13',3);
insert into tb_menu(id, title, parent) values(14, '一級菜單14',3);
insert into tb_menu(id, title, parent) values(15, '一級菜單15',4);
insert into tb_menu(id, title, parent) values(16, '一級菜單16',4);
insert into tb_menu(id, title, parent) values(17, '一級菜單17',4);
insert into tb_menu(id, title, parent) values(18, '一級菜單18',5);
insert into tb_menu(id, title, parent) values(19, '一級菜單19',5);
insert into tb_menu(id, title, parent) values(20, '一級菜單20',5);
--二級菜單
insert into tb_menu(id, title, parent) values(21, '二級菜單21',6);
insert into tb_menu(id, title, parent) values(22, '二級菜單22',6);
insert into tb_menu(id, title, parent) values(23, '二級菜單23',7);
insert into tb_menu(id, title, parent) values(24, '二級菜單24',7);
insert into tb_menu(id, title, parent) values(25, '二級菜單25',8);
insert into tb_menu(id, title, parent) values(26, '二級菜單26',9);
insert into tb_menu(id, title, parent) values(27, '二級菜單27',10);
insert into tb_menu(id, title, parent) values(28, '二級菜單28',11);
insert into tb_menu(id, title, parent) values(29, '二級菜單29',12);
insert into tb_menu(id, title, parent) values(30, '二級菜單30',13);
insert into tb_menu(id, title, parent) values(31, '二級菜單31',14);
insert into tb_menu(id, title, parent) values(32, '二級菜單32',15);
insert into tb_menu(id, title, parent) values(33, '二級菜單33',16);
insert into tb_menu(id, title, parent) values(34, '二級菜單34',17);
insert into tb_menu(id, title, parent) values(35, '二級菜單35',18);
insert into tb_menu(id, title, parent) values(36, '二級菜單36',19);
insert into tb_menu(id, title, parent) values(37, '二級菜單37',20);
--三級菜單
insert into tb_menu(id, title, parent) values(38, '三級菜單38',21);
insert into tb_menu(id, title, parent) values(39, '三級菜單39',22);
insert into tb_menu(id, title, parent) values(40, '三級菜單40',23);
insert into tb_menu(id, title, parent) values(41, '三級菜單41',24);
insert into tb_menu(id, title, parent) values(42, '三級菜單42',25);
insert into tb_menu(id, title, parent) values(43, '三級菜單43',26);
insert into tb_menu(id, title, parent) values(44, '三級菜單44',27);
insert into tb_menu(id, title, parent) values(45, '三級菜單45',28);
insert into tb_menu(id, title, parent) values(46, '三級菜單46',28);
insert into tb_menu(id, title, parent) values(47, '三級菜單47',29);
insert into tb_menu(id, title, parent) values(48, '三級菜單48',30);
insert into tb_menu(id, title, parent) values(49, '三級菜單49',31);
insert into tb_menu(id, title, parent) values(50, '三級菜單50',31);
commit;
2.查找所有上級節點
--查詢樹狀結構某節點(44)的上級所有根節點
with cte_parent(id,title,parent)
as
(
--起始條件
select id,title,parent
from tb_menu
where id = 44 --列出子節點查詢條件
union all
--遞歸條件
select a.id,a.title,a.parent
from tb_menu a
inner join
cte_parent b --執行遞歸，這裏就要理解下了
on a.id=b.parent
)
select * from cte_parent;
3.查找下級節點帶level
--查詢樹狀結構某節點下的所有子節點(
with cte_child(id,title,parent,level)
as
(
--起始條件
select id,title,parent,0 as level
from tb_menu
where id = 6--列出父節點查詢條件
union all
--遞歸條件
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;
參考文章
SQL Server 2008中的CTE遞歸查詢 http://www.cnblogs.com/xfrog/archive/2010/10/10/1847462.html
Oracle 樹操作(start with…connect by…prior) http://www.cnblogs.com/linjiqin/archive/2013/06/24/3152674.html
作者：小小程序員1986
來源：CSDN
原文：https://blog.csdn.net/jethai/article/details/52345361
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