两个select写法

select tag,concat(round(avg(t_per)*100,2),'%') avg_play_progress
from(
    select v.tag,if(timestampdiff(second,u.start_time,u.end_time)>v.duration,
                    1,
                    timestampdiff(second,u.start_time,u.end_time)/v.duration
                   ) t_per
    from tb_user_video_log u
    left join tb_video_info v on v.video_id=u.video_id
)t
group by tag
having avg(t_per)>0.6
order by avg(t_per) desc;