มีเที่ยวบินไปกลับจากแอตแลนต้าไปดัลลาสผ่านเดนเวอร์หรือไม่ ไม่จำเป็นต้องใช้ทุกโต๊ะ
is there a round trip flight from ATLANTA to DALLAS via DENVERIt is not neccessary to use all the tables.
 time_zone:  time_zone_code [ text]  time_zone_name [ text]  hours_from_gmt [ int] 
SELECT DISTINCT flight.flight_id FROM 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, fare, flight, flight_fare, flight_stop WHERE ((CITY_2.city_code = AIRPORT_SERVICE_2.city_code AND CITY_2.city_name = 'DENVER' AND NOT fare.round_trip_cost IS NULL AND flight_fare.fare_id = fare.fare_id AND flight_stop.stop_airport = AIRPORT_SERVICE_2.airport_code AND flight.flight_id = flight_fare.flight_id AND flight.flight_id = flight_stop.flight_id) AND CITY_1.city_code = AIRPORT_SERVICE_1.city_code AND CITY_1.city_name = 'DALLAS' AND flight.to_airport = AIRPORT_SERVICE_1.airport_code) AND CITY_0.city_code = AIRPORT_SERVICE_0.city_code AND CITY_0.city_name = 'ATLANTA' AND flight.from_airport = AIRPORT_SERVICE_0.airport_code