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