题解 | #平均播放进度大于60%的视频类别#

select tag,
concat(round(avg(if(timestampdiff(second,start_time,end_time)>=duration,100,timestampdiff(second,start_time,end_time)/duration*100)),2),'%') avg_play_progress
from tb_video_info tbv right join tb_user_video_log tbu on tbv.video_id=tbu.video_id
group by tag
having avg_play_progress>60
order by avg_play_progress desc;

各位大佬，想请教下，虽然我这样运行是通过的，但是为什么这里having avg_play_progress>60这样是可行么？？？就这个地方确实没看懂了