Category Spend Royalty :Rank Customers by Total Spending Within Each Product Category Advanced

          with customerspending as
  (select o.customerid,
          p.category,
          sum(od.quantity * p.price) as totalspending
   from orders o
   join orderdetails od on o.orderid = od.orderid
   join products p on od.productid = p.productid
   group by o.customerid,
            p.category)
select customerid,
       category,
       totalspending,
       row_number() over (partition by category
                          order by totalspending desc) as rank
from customerspending;