มีบริการขนส่งภาคพื้นดินใดบ้างที่สนามบินบอสตันไม่จำเป็นต้องใช้ตารางทั้งหมด
what ground transportation is available at the BOSTON airportIt is not neccessary to use all the tables.
 city:  city_code [ varchar]  city_name [ varchar]  state_code [ varchar]  country_name [ varchar]  time_zone_code [ varchar] 
SELECT DISTINCT ground_service.transport_type FROM airport, airport_service, city, ground_service WHERE airport.airport_code = airport_service.airport_code AND city.city_code = airport_service.city_code AND city.city_name = 'BOSTON' AND ground_service.airport_code = airport.airport_code