Updating multiple rows in a database

Hi,

I have a form with a list of currencies, displayed in a repeated container. I have a Currency table in my BDM and I want the users to be able to edit the exchange rate. I don't want multiple values in my database (inserting the new values of the exchange rates as new rows in the database is not acceptable), I want to update the rows of the currencies that the users update. How do I go about doing that? I have searched around and have not found a solution that I am able to use for my case. For now, I don't mind if the solution involves updating the whole table, and not checking whether or not the user had updated the value, if that is easier to be done.

Thank you in advance.