某网站包含两个表，Customers 表和 Orders 表。编写一个 SQL 查询，找出所有从不订购任何东西的客户。
Customers 表：
+----+-------+
| Id | Name |
+----+-------+
| 1 | Joe |
| 2 | Henry |
| 3 | Sam |
| 4 | Max |
+----+-------+
Orders 表：
+----+------------+
| Id | CustomerId |
+----+------------+
| 1 | 3 |
| 2 | 1 |
+----+------------+
例如给定上述表格，你的查询应返回：
+-----------+
| Customers |
+-----------+
| Henry |
| Max |
+-----------+
思路：使用左外连接
代码：
# Write your MySQL query statement below
select c.Name as Customers
from Customers as c left join Orders as o on c.Id=o.CustomerId
where CustomerId is null
另一种方法：
# Write your MySQL query statement below
select customers.name as `Customers`
from customers
where customers.id not in
(
select customerid from orders
);