LeetCode（数据库）- 兴趣相同的朋友

-- 解决方案(1)
select distinct a.user1_id, a.user2_id
  from Friendship a, Listens b, Listens c
 where a.user1_id = b.user_id
   AND a.user2_id = c.user_id
   AND b.song_id = c.song_id
   AND b.day = c.day
 group by a.user1_id, a.user2_id, b.day
having COUNT(distinct b.song_id) >= 3
-- 解决方案(2)
WITH t AS(SELECT * FROM Listens GROUP BY 1, 2, 3)
SELECT DISTINCT l1.user_id user1_id, l2.user_id user2_id
FROM t l1 JOIN t l2 ON l1.user_id < l2.user_id AND l1.day = l2.day
WHERE (l1.user_id, l2.user_id) IN (SELECT * FROM Friendship)
GROUP BY 1, 2, l1.day
HAVING COUNT(IF(l1.song_id = l2.song_id, 1, NULL)) >= 3