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

使用左外连接 然后使用条件语句

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

使用NOT IN

# Write your MySQL query statement belowSELECT C.Name Customers    FROM Customers C    WHERE C.Id NOT IN (SELECT CustomerId FROM Orders);