我怎样才能找到客户与数据库中没有订单？

Question

想象我有两个表：

客户（CUST_ID） 订单（ORDER_ID，CUST_ID）

我怎样才能得到所有谁没有任何订单的客户？

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，一个相关子查询将执行最佳

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

另一种选择是左连接/ 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有时提供的解决方案，以及

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

Check here的各种选择和相对优势进行了深入的讨论。

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

您可以选择从客户表所在的ID没有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; 

尝试在可能的情况下避免子查询 - 它们可能会造成可怕的性能下降。