Further aggregate results of a SQL query in BI Publisher RTF template

Summary:

I have successfully created a SQL query to report on the number and amount of unmatched transactions by period and aging bucket but it seems we are still seeing rows for the same period where either currencies differ or the transaction date is different. We would like to summarize these further in the BI Publisher RTF template as the SQL query, although working fine, has become very long and complex.

I created a RFT from the XML and want to insert an aggregate function but the tutorial is not very clear on how to do this. I do know that the grouping context is very important to keep in mind.