oracle 递归查询，向上和向下遍历

--查询全部资源信息
select * from urm_class_info
--向上遍历树，找到路径直到根节点，指定的是parentid
select distinct classid,parentid,name
from urm_class_info
start with parentid = 'cmdb0000000000000017'
connect by prior parentid = classid
--向上遍历树，找到路径直到根节点，指定的是classid，和下面的主要区别就是parentid和classid的位置
select classid,parentid,name
from urm_class_info
start with classid = 'cmdb0000000000000401'
connect by prior parentid = classid
--向下遍历整棵树，可以指定classid，来遍历指定节点的树
select classid,parentid,name
from urm_class_info
start with classid = 'cmdb0000000000000017'
connect by prior classid = parentid

--向下遍历整棵树，可以指定parentid，来遍历指定parentid节点的树，不包含parentid
select classid,parentid,name
from urm_class_info
start with parentid = 'cmdb0000000000000017'
connect by prior classid = parentid