leetcode-183-Customers-Who-Never-Order

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描述

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.

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

Table: Orders.

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

Using the above tables as example, return the following:

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

分析

两张表，一张 Customer，一张 Orders，通过这两张表找出没有订购过商品的顾客。

解决方案(MySQL)

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# Write your MySQL query statement below
SELECT 
C.Name as Customers 
FROM Customers C
WHERE C.Id not in 
(
    SELECT CustomerId FROM Orders 
)

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