题解 | #网易云音乐推荐(网易校招笔试真题)#

#1、从follow种找出user_id=1所关注的人 #2、从music_like种找出所关注人喜欢的音乐编号，去除出与1相同喜欢的相同编号的音乐 #3、查出为用户1所推荐的音乐

SELECT music_name from music where id in ( (SELECT music_id FROM music_likes where user_id IN (select follower_id from follow where user_id = 1) and music_id not in (SELECT music_id from music_likes where user_id = 1) GROUP BY music_id ORDER BY music_id) )

之前出错就是因为写成music_id != (SELECT music_id from music_likes where user_id = 1) 产生了笛卡儿积，就导致出错了