select
coalesce(tran_cou,0) as tran_cou,
sum(vis_cou) as vis_cou
from
(select user_id, visit_date,count(*) as vis_cou
from leetcode.ex_1336_visits
group by user_id,visit_date) a
left join
(select user_id,transaction_date,count(*) as tran_cou
from leetcode.ex_1336_transactions
group by user_id,transaction_date )b
on a.user_id=b.user_id and a.visit_date=b.transaction_date
GROUP BY coalesce(tran_cou,0)
;