题解 | #网易云音乐推荐(网易校招笔试真题)#

先查找user_id=1关注的用户和他喜欢的music_id

select follower_id from follow where user_id=1

select music_id from music_likes where user_id=1

再将用户喜欢的music_id和music_name表连接起来

select * 
from music_likes ml
left join music m 
on ml.music_id=m.id

最后查从user_id=1 关注的用户喜欢的music中除掉1用户喜欢的音乐

整合：

select distinct music_name
from music_likes ml
left join music m 
on ml.music_id=m.id
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)
order by m.id