-- Database schema
| airlines : uid [ INT ] primary_key , Airline [ TEXT ] , Abbreviation [ TEXT ] , Country [ TEXT ] | airports : City [ TEXT ] , AirportCode [ TEXT ] primary_key , AirportName [ TEXT ] , Country [ TEXT ] , CountryAbbrev [ TEXT ] | flights : Airline [ INT ] primary_key , FlightNo [ INT ] , SourceAirport [ TEXT ] flights.SourceAirport = airports.AirportCode , DestAirport [ TEXT ] flights.DestAirport = airports.AirportCode |
-- -- Find the name of airports which do not have any flight in and out.

SELECT AirportName FROM Airports WHERE AirportCode NOT IN (SELECT SourceAirport FROM Flights UNION SELECT DestAirport FROM Flights);