CREATE TABLE Flights (AirportName VARCHAR(255), AirportCode VARCHAR(255), SourceAirport VARCHAR(255), DestAirport VARCHAR(255)); CREATE TABLE Airports (AirportName VARCHAR(255), AirportCode VARCHAR(255), SourceAirport VARCHAR(255), DestAirport VARCHAR(255))
Find the name of airports which do not have any flight in and out.
    
SQL: SELECT AirportName FROM Airports WHERE NOT AirportCode IN (SELECT SourceAirport FROM Flights UNION SELECT DestAirport FROM Flights)