mysql 练习

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1 从不订购的客户

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       |
+-----------+
解答① 联接
select c.name as customers from customers c left join orders o on c.id = o.customerid where customerid is null
解答② not in
select c.name as customers from customers c where c.id not in (select customerid from orders)

mysql 练习

标签：HERE   customers   查询   pre   sam   客户   left join   tom   mys   

原文地址：https://www.cnblogs.com/islvgb/p/9428650.html