มีบริการขนส่งภาคพื้นดินประเภทใดบ้างในเดนเวอร์ไม่จำเป็นต้องใช้ตารางทั้งหมด
what types of ground transportation are available in DENVERIt is not neccessary to use all the tables.
 aircraft:  aircraft_code [ varchar]  aircraft_description [ varchar]  manufacturer [ varchar]  basic_type [ varchar]  engines [ int]  propulsion [ varchar]  wide_body [ varchar]  wing_span [ int]  length [ int]  weight [ int]  capacity [ int]  pay_load [ int]  cruising_speed [ int]  range_miles [ int]  pressurized [ varchar] 
SELECT DISTINCT ground_service.transport_type FROM city, ground_service WHERE city.city_name = 'DENVER' AND ground_service.city_code = city.city_code