题解 | #每个创作者每月的涨粉率及截止当前的总粉丝量#

-- 计算2021年里每个创作者每月的涨粉率及截止当月的总粉丝量
-- 涨粉率=(加粉量 - 掉粉量) / 播放量

-- 计算涨粉率和总粉丝数量
select 
author 
,month 
,round(fans_cnt/play_cnt,3) as fans_growth_rate 
,sum(fans_cnt) over(partition by author order by month) as total_fans 
from (
-- 1、先获取每个作者每个月的播放量、涨粉量 
select 
author 
,left(start_time,7) as month 
,count(1) as play_cnt 
,sum(case 
    when if_follow = 1 then 1 
    when if_follow = 2 then -1 
    else 0 
    end
) as fans_cnt 
from tb_user_video_log a 
left join tb_video_info b 
on a.video_id = b.video_id 
where year(start_time) = '2021'
group by author ,left(start_time,7) ) c 
order by author ,total_fans