select customer_id, product_id, product_name from

(

select o.customer_id, o.product_id, p.product_name,

rank() over (partition by customer_id order by count(o.product_id) desc) as ranking

from Orders o

join Products p

on o.product_id = p.product_id

group by customer_id, product_id

) tmp

where ranking = 1

order by customer_id, product_id