What are the customer ids for customers who do not have an account?
SELECT customer_id FROM Customers EXCEPT SELECT customer_id FROM Accounts
SELECT customer_id FROM Customers EXCEPT SELECT customer_id FROM Accounts
[{'customer_id': 1}, {'customer_id': 2}, {'customer_id': 4}, {'customer_id': 5}, {'customer_id': 7}, {'customer_id': 10}, {'customer_id': 11}, {'customer_id': 14}]