กราวด์ซานฟรานซิสโกไม่จำเป็นต้องใช้ตารางทั้งหมด
ground SAN FRANCISCOIt is not neccessary to use all the tables.
 fare:  fare_id [ int]  from_airport [ varchar]  to_airport [ varchar]  fare_basis_code [ text]  fare_airline [ text]  restriction_code [ text]  one_direction_cost [ int]  round_trip_cost [ int]  round_trip_required [ varchar] 
SELECT DISTINCT ground_service.transport_type FROM city, ground_service WHERE city.city_name = 'SAN FRANCISCO' AND ground_service.city_code = city.city_code