Approach: Using sub-query and
NOT IN clause [Accepted]
If we have a list of customers who have ever ordered, it will be easy to know who never ordered.
We can use the following code to get such list.
select customerid from orders;
Then, we can use
NOT IN to query the customers who are not in this list.
select customers.name as 'Customers' from customers where customers.id not in ( select customerid from orders );