Report showing abnormal information

[aggregate sum over the periods]

Hi, everyone,
I got a problem in the report.
I created two queries both linked to same table including ProductID,
SalesDate, SalesAmount. Query A is set for the period from Nov04 to Dec04 but
Query B for Nov04 to Jan05. I did so by insert one new column in query with
SalesDate1 in Query A and SalesDate2 in Query B. After this, I make a report
selecting these two queries as sources. As a result, the result is not
correct becasuse the information are greatly duplicated or even triplicated.
Who can advise me my error here.

Thanks, Roy