难点:筛选最近30天的数据

select tag,sum(if_retweet) as retweet_cnt,round(sum(if_retweet)/count(1),3) as retweet_rate
from tb_user_video_log t join tb_video_info t1 using(video_id)
where start_time BETWEEN date_add((select max(start_time) from tb_user_video_log),interval -30 day) and (select max(start_time) from tb_user_video_log) 
group by tag
order by retweet_rate desc