ค่าตั๋วไปกลับชั้น FIRST ระหว่าง OAK และ ATL คืออะไรไม่จำเป็นต้องใช้ตารางทั้งหมด
what is the cost of a round trip ticket FIRST class between OAK and ATLIt is not neccessary to use all the tables.
 flight_leg:  flight_id [ int]  leg_number [ int]  leg_flight [ int] 
SELECT DISTINCT fare.fare_id FROM airport AS AIRPORT_0, airport AS AIRPORT_1, fare, fare_basis, flight, flight_fare WHERE (AIRPORT_0.airport_code = 'OAK' AND AIRPORT_1.airport_code = 'ATL' AND fare_basis.class_type = 'FIRST' AND fare.fare_basis_code = fare_basis.fare_basis_code AND flight_fare.fare_id = fare.fare_id AND flight.flight_id = flight_fare.flight_id AND flight.from_airport = AIRPORT_0.airport_code AND flight.to_airport = AIRPORT_1.airport_code) AND NOT fare.round_trip_cost IS NULL