โปรดแสดงสายการบินที่มีเที่ยวบินจากเดนเวอร์ไปบอสตันโดยแวะที่ฟิลาเดลเฟีย ไม่จำเป็นต้องใช้ตารางทั้งหมด
please show me airlines with flights from DENVER to BOSTON with stop in PHILADELPHIAIt is not neccessary to use all the tables.
 flight_stop:  flight_id [ int]  stop_number [ int]  stop_days [ text]  stop_airport [ text]  arrival_time [ int]  arrival_airline [ text]  arrival_flight_number [ int]  departure_time [ int]  departure_airline [ text]  departure_flight_number [ int]  stop_time [ int] 
SELECT DISTINCT airline.airline_code FROM airline, airport_service AS AIRPORT_SERVICE_0, airport_service AS AIRPORT_SERVICE_1, airport_service AS AIRPORT_SERVICE_2, city AS CITY_0, city AS CITY_1, city AS CITY_2, flight, flight_stop WHERE (CITY_1.city_code = AIRPORT_SERVICE_1.city_code AND CITY_1.city_name = 'BOSTON' AND CITY_2.city_code = AIRPORT_SERVICE_2.city_code AND CITY_2.city_name = 'PHILADELPHIA' AND flight_stop.stop_airport = AIRPORT_SERVICE_2.airport_code AND flight.flight_id = flight_stop.flight_id AND flight.to_airport = AIRPORT_SERVICE_1.airport_code) AND CITY_0.city_code = AIRPORT_SERVICE_0.city_code AND CITY_0.city_name = 'DENVER' AND flight.airline_code = airline.airline_code AND flight.from_airport = AIRPORT_SERVICE_0.airport_code