PL/SQL：有条件的 Where

Question

我有以下场景：

CREATE OR REPLACE PROCEDURE GETINBOX
(
    inHasAttachments        IN int
)
AS

BEGIN

    SELECT M.MailId,
           M.SenderId,
           E.Emp_Name As "Sender",
           MI.RecipientId,
           M.Subject

    FROM MAIL M INNER JOIN MAILINBOX MI ON M.MailId = MI.MailId


    WHERE MI.RecipientId = '547' AND
          M.NotificationSelected = 'Y'

    IF inHasAttachments = '1' THEN
       AND M.Attachments = 'Y'
    END IF;


END GETINBOX;

是否可以根据参数的值在where子句中添加条件？

    WHERE MI.RecipientId = '547' AND
          M.NotificationSelected = 'Y'

    IF inHasAttachments = '1' THEN
       AND M.Attachments = 'Y'
    END IF;

显然这是不允许的，但在 PL/SQL 中是否可以通过某种方式做到这一点？ 我知道一种方法是复制查询并根据参数的值执行不同的查询，但我不想复制我的代码。

Answer 1

据我了解您的要求：如果参数inHasAttachments 的值是1，那么您想通过M.Attachments = 'Y' 进一步过滤，如果它的值不是1，那么您不关心@ 987654325@。这是条件MI.RecipientId = '547' AND M.NotificationSelected = 'Y'的补充。

你可以这样做：

SELECT M.MailId,
   M.SenderId,
   E.Emp_Name As "Sender",
   MI.RecipientId,
   M.Subject
FROM MAIL M INNER JOIN MAILINBOX MI ON M.MailId = MI.MailId
WHERE MI.RecipientId = '547' AND M.NotificationSelected = 'Y'
  AND (inHasAttachments <> '1' OR M.Attachments = 'Y')