# 查询向user_id = 1 的用户，推荐其关注的人喜欢的音乐。
with musci_likes as 
(select user_id,music_id
from music_likes
where music_id not in 
(select music_id
from music_likes
where user_id=1
)
)

select a.music_name
from
(select distinct a3.id,a3.music_name
from
(select follower_id
from follow
where user_id=1
) as a1
inner join
musci_likes as a2 on a1.follower_id=a2.user_id
inner join
music as a3 on a2.music_id=a3.id
order by a3.id asc
) as a