select city_category, user_id, avg(purchase) as average_purchase, dense_rank() over(partition by city_category order by user_id desc)
	from blackfriday b
    group by b.user_id, city_category
        having avg(purchase) > ( select avg(purchase)
									from blackfriday a
									where a.city_category = b.city_category
									group by city_category)
    order by b.city_category, user_id
    ;