Mysql__leecode/0183.从不订购的客户_mysql出现0183-优快云博客

本文解析如何使用SQL（notin和left join方法）从Customers和Orders表中筛选出从未下单的客户，适合SQL初学者和数据库管理实践者。

183. 从不订购的客户

二、解题方法
- 1.方法一：not in
- 2.方法二：left in

一、刷题内容

原题链接

https://leetcode-cn.com/problems/customers-who-never-order/

内容描述

SQL架构
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       |
+-----------+

二、解题方法

1.方法一：not in

# Write your MySQL query statement below
select 
    Customers.Name as Customers from Customers
where 
    Customers.Id not in (
        select 
            CustomerId 
        from 
            Orders
        );

2.方法二：left in

# Write your MySQL query statement below
select a.Name as Customers
from Customers as a
left join Orders as b
on 
	a.Id=b.CustomerId
where 
	b.CustomerId is null;