**I've edited the question***

If an account has a certain currency (for example, a bank account) - is it possible that there is a transaction with a different currency?

If so - how to calculate the balance of an account in the ACCOUNT's currency (not transaction currency, not base currency, not accounting book currency, but the currency which is defined for that account)

A little context: I am trying to calculate the balance in the bank accounts' currency via ODBC queries.

So I wonder if I sum the foreignamount field - will it return the value I need.

As I understand, the foreignamount is in the TRANSACTION CURRENCY, not in ACCOUNT CURRENCY so if there are any transactions in a currency which is different from the bank account's currency, the result will be wrong.