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183. Customers Who Never Order

183. Customers Who Never Order

作者: 无敌的肉包 | 来源:发表于2018-06-07 12:00 被阅读0次

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:

SELECT Name as 'Customers'
FROM Customers 
WHERE Customers.Id NOT IN(
SELECT CustomerId
FROM Orders)

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