database - 查找没有连接匹配的记录

Question

我有一个邮件收件人表，通过 many2many 表（recipients_mails）链接到邮件消息表。每次发送邮件时，我都会在 many2many 表中添加一行。

我需要知道哪些收件人没有收到 ID 为 n 的电子邮件。3.

桌子是这样雕刻的：

Recipients
recipient_id, email

Recipients_mails
recipient_fk, mail_fk

Mails
mail_id, content etc.

非常感谢

Answer 1

SELECT  *
FROM    recipients
WHERE   NOT EXISTS
        (
        SELECT  NULL
        FROM    recipients_mails
        WHERE   (recipient_fk, mail_fk) = (recipient_id, 3)
        )