Question

我有两个表：customer和mailing：

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

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

我想要一个sql调用，返回尚未收到某个邮件的所有客户。怎么样？

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

像

这样的东西

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

您所描述的内容称为ANTI JOIN。通常在SQL中有三种不同的方法：带有子查询的NOT IN条件，带有相关子查询的NOT EXISTS条件或带有LEFT JOIN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

This blog post比较MySQL 5.1的不同可能性。根据它，LEFT JOIN / IS NULL和NOT IN比NOT EXISTS快。
但是，你应该自己尝试哪一个是最快的。这总取决于您的数据，索引......

用于连接的SQL语句，但不在其他表中

4 个答案: