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183. Customers Who Never Order

Description

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

Solution

  • mysql
/*
 Success Detail:
 Runtime: 253 ms, faster than 87.43% of MySQL online submissions for Customers Who Never Order.
 Memory Usage: 0 MB, less than 100% of MySQL online submissions for Customers Who Never Order.
 */
select Name as Customers 
from Customers 
where id not in(select CustomerId from Orders)