prior放的左右位置决定了检索是自底向上还是自顶向下. 左边是自上而下（找子节点），右边是自下而上（找父节点）
SELECT T.AREA_CODE, T.AREA_NAME, T.AREA_LEVEL FROM TBL_SYS_AREA_CODE T CONNECT BY PRIOR T.AREA_CODE = T.PARENT_AREA_CODE START WITH T.PARENT_AREA_CODE = ‘父级‘;
SELECT T.AREA_CODE, T.AREA_NAME, T.AREA_LEVEL FROM TBL_SYS_AREA_CODE T CONNECT BY T.AREA_CODE = PRIOR T.PARENT_AREA_CODE START WITH T.Area_Name = ‘子级‘;