instruction: is the AA flight 813 from BOSTON to OAKLAND a nonstop flight
response: SELECT DISTINCT flight.flight_id FROM airport_service AS AIRPORT_SERVICE_0, airport_service AS AIRPORT_SERVICE_1, city AS CITY_0, city AS CITY_1, flight WHERE (((CITY_1.city_code = AIRPORT_SERVICE_1.city_code AND CITY_1.city_name = 'OAKLAND' AND flight.flight_number = 813 AND flight.to_airport = AIRPORT_SERVICE_1.airport_code) AND CITY_0.city_code = AIRPORT_SERVICE_0.city_code AND CITY_0.city_name = 'BOSTON' AND flight.from_airport = AIRPORT_SERVICE_0.airport_code) AND flight.stops = 0) AND flight.airline_code = 'AA'