สนามบินอยู่ห่างจากตัวเมือง PITTSBURGH แค่ไหนไม่จำเป็นต้องใช้โต๊ะทั้งหมด
how far is the airport from downtown PITTSBURGHIt is not neccessary to use all the tables.
 dual_carrier:  main_airline [ varchar]  low_flight_number [ int]  high_flight_number [ int]  dual_airline [ varchar]  service_name [ text] 
SELECT DISTINCT airport_service.miles_distant FROM airport_service, city WHERE city.city_code = airport_service.city_code AND city.city_name = 'PITTSBURGH'