题解 | #广告点击的高峰期#

select new.time click_hour, new.count click_cnt
from(
select date_format(click_time, '%H') time, row_number()over(order by sum(trace_id) desc) as rk, count(trace_id) count
from user_ad_click_time
group by date_format(click_time, '%H') 
) new
where new.rk = 1