先前連接

Question

如何突破第三次嵌套的查詢？

 SELECT CHILD_ID
   FROM COLLECTION_ITEMS 
  START WITH PARENT_ID = 16917 
CONNECT BY PRIOR CHILD_ID = PARENT_ID

我有這樣的查詢，如果嵌套增加到三個以上我必須結束查詢。

Answer 1

您可以使用LEVEL偽列。

SELECT
  CHILD_ID
FROM
  COLLECTION_ITEMS
WHERE
  LEVEL <= 3
  START WITH PARENT_ID      = 16917
  CONNECT BY PRIOR CHILD_ID = PARENT_ID