I am currently creating an Access 2007 database for calculating salesperson commissions. I have a table with 5 fields I'm working with: SalesRep, SOWRep, TerritoryRep, Period and Commission. I am trying to build a query that will calculate commission for a salesperson for each record where their name appears in one of the first three fields. Each time their name appears, they get the commission listed in the Commission field for the stated Period. I have managed to do this part successfully. My problem now is that I am creating a query that will sum all of their commissions by Period. I have run into a situation where sometimes a salesperson will not appear in one of the rep fields, resulting in NULL values in the previous queries. How can I create a final query that will sum correctly even if there are NULL values returned on the previous queries?