LeetCode Database 183 从不订购的客户

1. 题目描述

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       |
+-----------+

2. 题解

2.1. MySQL (NOT IN)

SELECT tb1.Name AS Customers FROM Customers tb1
WHERE tb1.Id NOT IN (
    SELECT DISTINCT(tb2.CustomerId) FROM Orders tb2
)

MySQL（LEFT JOIN）

SELECT tb1.Name AS Customers FROM Customers tb1
LEFT JOIN Orders tb2
ON tb1.Id = tb2.CustomerId
WHERE tb2.Id IS NULL