แสดงเมืองที่ให้บริการโดย CPIt ไม่จำเป็นต้องใช้ตารางทั้งหมด
show me the cities served by CPIt is not neccessary to use all the tables.
 food_service:  meal_code [ text]  meal_number [ int]  compartment [ text]  meal_description [ varchar] 
SELECT DISTINCT city.city_code FROM airport_service, city, flight WHERE city.city_code = airport_service.city_code AND flight.airline_code = 'CP' AND flight.from_airport = airport_service.airport_code