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 |
+———–+

解答：找出数据中没有下过订单的顾客：

  • 子查询：
# Write your MySQL query statement below
SELECT Name AS Customers  FROM customers WHERE id NOT IN(SELECT customerId FROM orders);
  • 联表查询：
SELECT c1.Name AS Customers FROM Customers c1 LEFT JOIN Orders b on c1.Id = b.CustomerId WHERE b.CustomerId is null;