LeetCode-183.从不订购的客户

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。

表: Customers

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

表: Orders

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

返回如下结果

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

添加表结构和数据

DROP TABLE IF EXISTS `customers`;
CREATE TABLE `customers`  (
  `Id` int(11) NOT NULL,
  `Name` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  PRIMARY KEY (`Id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Compact;

INSERT INTO `customers` VALUES (1, 'Joe');
INSERT INTO `customers` VALUES (2, 'Henry');
INSERT INTO `customers` VALUES (3, 'Sam');
INSERT INTO `customers` VALUES (4, 'Max');
--------------------------------------------------------------------------------------------
DROP TABLE IF EXISTS `orders`;
CREATE TABLE `orders`  (
  `Id` int(11) NOT NULL,
  `CustomerId` int(11) NULL DEFAULT NULL,
  PRIMARY KEY (`Id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Compact;

INSERT INTO `orders` VALUES (1, 3);
INSERT INTO `orders` VALUES (2, 1);

思路：

解答：

SELECT NAME AS Customers FROM customers 
WHERE id NOT IN ( SELECT customerid FROM orders )