mysql - 用于连接但不在其他表中的 SQL 语句

Question

我有两张桌子：customer和mailing：

+==========+  +=============+
| customer |  | mailing     |
+==========+  +=============+
| id       |  | id          |
+----------+  +-------------+
| name     |  | customer_id |
+----------+  +-------------+
              | mailing_id  |
              +-------------+

每次我向客户发送邮件时，我都会在邮件表中使用该邮件 ID 添加一行。一封邮件可以发送给多个客户。

我想要一个 sql 调用来返回所有尚未收到特定邮件的客户。如何 ？

我正在使用 mysql

Answer 1

select * from customer where id not in (
    select customer_id from mailing where mailing_id = @mailing_id
)

Answer 2

SELECT * FROM customers c
JOIN mailings m
ON c.id = m.id
WHERE NOT EXISTS (
    SELECT id
    FROM mailings i
    WHERE i.id = c.id
    GROUP BY i.id
)

Answer 3

就像是

Select c.ID, c.Name
From Customers C
left Join mailing m On c.id = m.customer_id
where m.customer_id is null

Answer 4

您所描述的称为ANTI JOIN. 通常在 SQL 中有三种不同的方式来制定它：NOT IN带有子查询的NOT EXISTS条件、带有相关子查询的条件或LEFT JOIN带有条件的NOT NULL条件。因此，对于您的查询，可能性是：

SELECT *
FROM customer
WHERE id NOT IN
    ( SELECT customer_id
     FROM mailing)

SELECT *
FROM customer c
WHERE NOT EXISTS
    ( SELECT customer_id
     FROM mailing m
     WHERE m.customer_id = c.id)

SELECT *
FROM customer c
LEFT JOIN mailing m ON c.id = m.customer_id
WHERE m.customer_id IS NULL

这篇博文比较了 MySQL 5.1 的不同可能性。据它说，LEFT JOIN / IS NULL并且NOT IN比NOT EXISTS.
但是，您应该自己尝试哪一个是最快的。这始终取决于您的数据、索引、...