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

查找所有从不订购任何东西的客户。

MySQL(821ms):

 # Write your MySQL query statement below
 SELECT Name AS Customers
 FROM Customers
 WHERE Id NOT IN (SELECT CustomerId
                  FROM Orders) ;

MySQL(803ms):  左外连接

 # Write your MySQL query statement below
 SELECT C.Name AS Customers
 FROM Customers AS C LEFT JOIN Orders AS O
   ON C.Id = O.CustomerId
 WHERE O.CustomerId IS NULL ;