如何使CONNECT BY参数可选

Question

我有一个程序使用Connect By

SELECT <lots of fields>
FROM Group g
  <joins>
WHERE <where>
CONNECT BY PRIOR g.ID = g.ParentID
START WITH g.ID = 1337
ORDER SIBLINGS BY g.Name
;

数字1337是这个过程的一个参数，如果这个值是0，我想忽略connect by代码并执行其他所有内容。

我该如何处理?

Answer 1

最明显的答案是测试connect by子句中的异常值:

SELECT <lots of fields>
FROM Group g
  <joins>
WHERE <where>
CONNECT BY PRIOR g.ID = g.ParentID and :param <> 0
START WITH g.ID = :param or :param = 0
ORDER SIBLINGS BY g.Name;