oracle 遞歸查詢，向上和向下遍歷

--查詢全部資源信息 
select * from urm_class_info 
--向上遍歷樹，找到路徑直到根節點，指定的是parentid 
select distinct classid,parentid,name 
from urm_class_info 
start with parentid = 'cmdb0000000000000017' 
connect by prior parentid = classid 
--向上遍歷樹，找到路徑直到根節點，指定的是classid，和下面的主要區別就是parentid和classid的位置 
select classid,parentid,name 
from urm_class_info 
start with classid = 'cmdb0000000000000401' 
connect by prior parentid = classid 
--向下遍歷整棵樹，可以指定classid，來遍歷指定節點的樹 
select classid,parentid,name 
from urm_class_info 
start with classid = 'cmdb0000000000000017' 
connect by prior classid = parentid 
--向下遍歷整棵樹，可以指定parentid，來遍歷指定parentid節點的樹，不包含parentid 
select classid,parentid,name 
from urm_class_info 
start with parentid = 'cmdb0000000000000017' 
connect by prior classid = parentid