I have a table, 'Customer_Orders' that basically lists the products purchased by customers across marketplaces (UK, DE, US etc). Here's a short overview of the table:
select cust_id, marketplace,
(count(*) - max(case when marketplace = 'UK' then count(*) end) over (partition by cust_id)) as diff_from_uk
from Customer_Orders co
group by cust_id, marketplace;