解题思路
第一个表的关注者是第二个表的被关注者，对第二个表的关注者计数
select f1
.follower
,count(distinct f2
.follower
) as num
from follow f1
,follow f2
where f1
.follower
=f2
.followee
group by f1
.follower
select followee
as follower
,count(distinct follower
) as num
from follow
where followee
in (select follower
from follow
)
group by followee
