LeetCode（数据库）- 查询具有最多共同关注者的所有两两结对组

-- 解决方案(1)
select a.user1_id,a.user2_id
  from (select a.user_id user1_id,
               b.user_id user2_id,
               rank() over(order by COUNT(1) desc) rn
          from Relations a, Relations b
         where a.user_id < b.user_id
           AND a.follower_id = b.follower_id
         group by a.user_id, b.user_id) A
 WHERE A.rn = 1
-- 解决方案(2)
WITH t AS(SELECT r1.user_id user1_id, r2.user_id user2_id, COUNT(*) cnt
FROM Relations r1 JOIN Relations r2 ON r1.user_id < r2.user_id AND r1.follower_id = r2.follower_id
GROUP BY 1, 2
ORDER BY 3 DESC)
SELECT user1_id, user2_id
FROM t
WHERE (SELECT MAX(cnt) FROM t) = cnt