题解 | #广告点击的高峰期#

select click_hour, click_cnt
from (select hour(click_time)                            click_hour,
             count(trace_id)                             click_cnt,
             rank() over (order by count(trace_id) desc) click_rank
      from user_ad_click_time
      group by hour(click_time)) as t
where click_rank = 1
;