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):
1 # Write your MySQL query statement below 2 SELECT Name AS Customers 3 FROM Customers 4 WHERE Id NOT IN (SELECT CustomerId 5 FROM Orders) ;
MySQL(803ms): 左外连接
1 # Write your MySQL query statement below 2 SELECT C.Name AS Customers 3 FROM Customers AS C LEFT JOIN Orders AS O 4 ON C.Id = O.CustomerId 5 WHERE O.CustomerId IS NULL ;