614 Second Degree Follower

https://nifannn.github.io/2017/10/27/SQL-Notes-Leetcode-614-Second-Degree-Follower/

select followee f1.follower, count(f1.follower) num from follow f1

join  follow f2 on f1.followee  = f2.follower

group by f1.followee

order by f1.followee;