oracle樹形結構遍歷

數據庫樹形結構，正反遍歷

--從Root往樹末梢遞歸
select level ,identity,pid from table_name
　　start with identity=475
　　connect by prior identity = pid

--從末梢往樹ROOT遞歸
select level ,identity,pid,yylevel from table_name
　　start with identity=542
　　connect by prior pid = identity