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 | +———–+
Link: https://leetcode.com/problems/customers-who-never-order/
Solution 1 #
select Name as Customers from Customers where Id not in (select CustomerId from Orders);
Solution 2 #
select C.Name as Customers from Customers C left join Orders O on C.Id = O.CustomerId where O.CustomerId is null;