## 题目
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       |
+-----------+
```

## 答案
```sql
select Name as Customers
from Customers a
where a.id not in (select CustomerId from Orders)
```