用于联接但不在其他表中的SQL语句

Question

I have two tables: customer and mailing :

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

Every time I send a mailing to a customer, I add a row in the mailings table with that mailing id. One mailing can be sent to multiple customers.

I want to have a sql call that returns all customers that have not yet received a certain mailing. How to ?

I am using 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

Something like

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

What you describe is called an ANTI JOIN . Usually there are three different ways for formulating it in SQL: A NOT IN condition with a subquery, a NOT EXISTS condition with a correlated subquery, or a LEFT JOIN with a NOT NULL condition. So for your query the possibilities are:

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 compares the different possibilities with MySQL 5.1. According to it, LEFT JOIN / IS NULL and NOT IN are faster than NOT EXISTS .
However, you should try for yourself which one is the fastest. That always depends on your data, indexes, ...