题目链接：点击打开链接
题目大意：略。
解题思路：略。
AC 代码
WITH t AS(SELECT departure_airport id, flights_count cnt FROM Flights
UNION ALL
SELECT arrival_airport, flights_count FROM Flights),
tt AS(SELECT id, RANK() OVER(ORDER BY SUM(cnt) DESC) rk
FROM t
GROUP BY 1)
SELECT id airport_id
FROM tt
WHERE rk = 1
