Executing API with a Select?

I am trying to write a select statement to an Oracle database that includes a call to an API to return a value. For example

Select ORDER_NUMBER, Currency_Rate_Api.Get_Currency_Rate('Company', 'USD', '1', '2008-01-01') AS USD_Amount
FROM ORDER_TABLE

where the underline is the API that I am trying to run. I am struggling with the syntax to execute this or if it's even possible??? I appreciate any assistance.

Thanks,
JB

re: Executing API with a Select?

what kind of API are you referring to? a simple pl/sql function is technically an API. what is the underlying functionality behind the API you are putting together?