ลูกค้าและพนักงานใช้นามสกุลอะไร?ไม่จำเป็นต้องใช้ทุกตาราง
What are the last names that are used by customers and staff?It is not neccessary to use all the tables.
 customer_payments:  customer_id [ number]  datetime_payment [ time]  payment_method_code [ text]  amount_payment [ number] 
SELECT last_name FROM customers INTERSECT SELECT last_name FROM staff