ค่าโดยสารไปกลับที่ถูกที่สุดจาก ATLANTA ถึง BWI คือเท่าไร ไม่จำเป็นต้องใช้ตารางทั้งหมด
what 's the lowest round trip fare from ATLANTA to BWIIt is not neccessary to use all the tables.
 restriction:  restriction_code [ text]  advance_purchase [ int]  stopovers [ text]  saturday_stay_required [ text]  minimum_stay [ int]  maximum_stay [ int]  application [ text]  no_discounts [ text] 
SELECT DISTINCT fare.fare_id FROM airport, airport_service, city, fare, flight, flight_fare WHERE airport.airport_code = 'BWI' AND city.city_code = airport_service.city_code AND city.city_name = 'ATLANTA' AND fare.round_trip_cost = (SELECT MIN(FAREalias1.round_trip_cost) FROM airport AS AIRPORTalias1, airport_service AS AIRPORT_SERVICEalias1, city AS CITYalias1, fare AS FAREalias1, flight AS FLIGHTalias1, flight_fare AS FLIGHT_FAREalias1 WHERE AIRPORTalias1.airport_code = 'BWI' AND CITYalias1.city_code = AIRPORT_SERVICEalias1.city_code AND CITYalias1.city_name = 'ATLANTA' AND FLIGHT_FAREalias1.fare_id = FAREalias1.fare_id AND FLIGHTalias1.flight_id = FLIGHT_FAREalias1.flight_id AND FLIGHTalias1.from_airport = AIRPORT_SERVICEalias1.airport_code AND FLIGHTalias1.to_airport = AIRPORTalias1.airport_code) AND flight_fare.fare_id = fare.fare_id AND flight.flight_id = flight_fare.flight_id AND flight.from_airport = airport_service.airport_code AND flight.to_airport = airport.airport_code