connect by prior start with 经常会被用到一个表中存在递归关系的时候。比如我们经常会将一个比较复杂的目录树存储到一个表中。或者将一些部门存储到一个表中，而这些部门互相有隶属关系。这个时候你就会用到connect by prior start with。
表结构：
create table TB_ORG
(
ORGID VARCHAR2(50) not null,
ORGNAME VARCHAR2(100),
ORGPARENT VARCHAR2(50),
)
SQL> select orgid,ORGPARENT from tb_org order by ORGid desc;
ORGID ORGPARENT
----------------- --------------------------------------------------
top_org
newsroom top_org
sjgt newsroom
bgjsyj newsroom
bgjs newsroom
test52 bgjsyj
test36 bgjsyj
test3 bgjs
test2 sjgt
test1 sjgt
tes4t1 bgjs
--子取父
select * from tb_org CONNECT BY PRIOR orgparent=orgid START WITH orgid='newsroom'
-----子取父变形 （）
select * from tb_org CONNECT BY PRIOR orgparent=orgid START WITH orgparent='newsroom'
--父取子（结果中没有父这条记录）
select * from tb_org CONNECT BY PRIOR orgid=orgparent START WITH orgparent='newsroom'
-----父取子变形（多了父这一级）
select * from tb_org connect by prior orgid=orgparent start with orgid ='newsroom'
注意orgid=orgparent 和orgparent=orgid
ref:http://blog.csdn.net/kenny1985/article/details/3980583