เที่ยวบินใดที่ออกจากเดนเวอร์ก่อน 12.00 น. บน NWไม่จำเป็นต้องใช้ตารางทั้งหมด
what flights leave DENVER before 1200 on NWIt is not neccessary to use all the tables.
 flight:  aircraft_code_sequence [ text]  airline_code [ varchar]  airline_flight [ text]  arrival_time [ int]  connections [ int]  departure_time [ int]  dual_carrier [ text]  flight_days [ text]  flight_id [ int]  flight_number [ int]  from_airport [ varchar]  meal_code [ text]  stops [ int]  time_elapsed [ int]  to_airport [ varchar] 
SELECT DISTINCT flight.flight_id FROM airport_service, city, flight WHERE (city.city_code = airport_service.city_code AND city.city_name = 'DENVER' AND flight.departure_time < 1200 AND flight.from_airport = airport_service.airport_code) AND flight.airline_code = 'NW'