183. 从不订购的客户

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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：

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+----+-------+
| Id | Name  |
+----+-------+
| 1  | Joe   |
| 2  | Henry |
| 3  | Sam   |
| 4  | Max   |
+----+-------+

Orders表

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+----+------------+
| Id | CustomerId |
+----+------------+
| 1  | 3          |
| 2  | 1          |
+----+------------+

例如给定上述表格，你的查询应返回：

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+-----------+
| Customers |
+-----------+
| Henry     |
| Max       |
+-----------+

解法

解法一：

先从订单表中找出所有已经订购过的客户，然后排除掉这些客户即可，注意表头别名

SQL

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select name  as Customers from customers where id not in (select customerId from orders);
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