递归查询 start with connect by prior

1、语法：start with 子节点ID='...' connect by prior 子节点ID = 父节点ID

含义：查询结果我所有的后代节点（包括我）

例子：

select id,parent_id
   from T_SM_MENU
　　start with id = 'dqs'
          connect by prior id = parent_id

2、语法：start with 子节点ID='...' connect by 子节点ID = prior 父节点ID

含义：查询结果我所有的前代节点（包括我）

例子：

select id,parent_id
from T_SM_MENU
start with id = 'dqs'
connect by id =prior parent_id

3、语法：start with 父节点ID='...' connect by prior 子节点ID = 父节点ID

含义：查询结果我所有的后代节点（不包括我）

例子：

select id,parent_id
from T_SM_MENU
start with id = 'dsm'
connect by prior id = parent_id

4、语法：start with 父节点ID='...' connect by 子节点ID = prior 父节点ID

含义： 

例子：

select id,parent_id
from T_SM_MENU
start with id = 'dsm'
connect by id =prior parent_id