27-second-longest-flight.sql

WITH ranked_flights as (
    SELECT *, 
           ROW_NUMBER() OVER(PARTITION BY LEAST(source_location, destination_location), 
                                          GREATEST(source_location, destination_location) 
                             ORDER BY flight_end - flight_start DESC) AS rn
    FROM   flights
)
SELECT id, destination_location, source_location, flight_start, flight_end
FROM   ranked_flights
WHERE  rn=2