語法:
--向下遞歸遍歷
select * from tablename start with cond1
connect by cond2
where cond3;
select *
from Table
start with id = 1 //以哪個ID爲開始,即跟節點ID
connect by prior id = parent_id //鏈接通過前一個ID和現在的父ID相等,定義子節點和父節點的關係
order by id ; //排個序