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（的cust_id） 订单（ORDER_ID，的cust_id）

如何让所有没有订单的客户获得？

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，相关子查询会表现最佳

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);

Check here深入讨论各种选项和相对优势。

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

您可以从customers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;

尝试尽可能避免子查询 - 它们可能会造成严重的性能损失。