I am trying to sort my table based on a field then add another field to
represent the rank(row number within the table).
I used to use RunSum function which does not exist in Firebird.

Select ItemDescription, Price, RunSum(1) as Rank from ItemsSales Order
by Price Desc

This query will give me the list of my products and the sale price in
order. The order is made through the "RANK" field. I need the rank
because my result is going on a report.
What is the easiest way to do this in Firebird?
Thank you,
-Halim