_1322.sql

--# Write your MySQL query statement below
select ad_id,
ifnull(
    round(
        avg(
            case
                when action = "Clicked" then 1
                when action = "Viewed" then 0
                else null
            end
        ) * 100,
    2),
0)
as ctr
from Ads
group by ad_id
order by ctr desc, ad_id asc;