【MySQL】【leetcode】 Customers Who Never Order解題報告

題目

Suppose that a website contains two tables, the Customers table and the Orders table. Write a SQL query to find all customers who never order anything.

Table: Customers.

+—-+——-+
| Id | Name |
+—-+——-+
| 1 | Joe |
| 2 | Henry |
| 3 | Sam |
| 4 | Max |
+—-+——-+
Table: Orders.

+—-+————+
| Id | CustomerId |
+—-+————+
| 1 | 3 |
| 2 | 1 |
+—-+————+
Using the above tables as example, return the following:

+———–+
| Customers |
+———–+
| Henry |
| Max |
+———–+
題目來源：https://leetcode.com/problems/customers-who-never-order/

代碼

找出沒有買東西的那些人的名字。

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