183. Customers Who Never Order

时间:2024-09-19 12:07:14

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 ;