[LeetCode MySQL] 183. Customers Who Never Order

183. Customers Who Never Order

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

 

QUERY

select c.name Customers
from customers c left join orders o
on c.id = o.customerid
where o.id is null

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Reference: 183. Customers Who Never Order