mysql - 如何在数据库中找到没有订单的客户？

Question

想象一下我有两张桌子：

客户(cust_id) 订单(order_id,cust_id)

如何获取所有没有订单的客户？

示例数据库：

customers
cust_id
1
2
3
4

orders
order_id customer_id
1        1
2        2
3        3
4        3

So what I want to retrieve is:

cust_id
4

Answer 1

通常，相关子查询会执行得最好

select cust_id
from customers
where not exists (select * from orders
                  where orders.customer_id = customers.cust_id);

另一个选项是 LEFT join/NOT NULL 组合

select c.cust_id
from customers c
left join orders o on o.customer_id = c.cust_id
where o.customer_id is null;

NOT IN 有时也作为解决方案提供

select c.cust_id
from customers c
where c.cust_id NOT IN (select distinct customer_id from orders);

在这里查看对各种选项和相对优势的深入讨论。

Answer 2

SELECT c.cust_id
FROM customers AS c
LEFT JOIN orders AS o
ON c.cust_id=o.customer_id
WHERE o.customer_id IS NULL;

Answer 3

您从客户表中选择 ID 未出现在订单表中的所有行

select * FROM customers where cust_id NOT IN 
   (select customer_id FROM orders)

Answer 4

SELECT  a.*
FROM    Customers a
        LEFT JOIN Orders b
            ON a.Cust_ID = b.Customer_ID
WHERE   b.Customer_ID IS NULL

Answer 5

试试这个

select * from customers where cust_id not in (select distinct customer_id from orders)

Answer 6

select c.cust_id
from customers c
left join orders o on o.customer_id = c.cust_id
where o.customer_id is null;

尽量避免子查询 - 它们可能会严重影响性能。