I'm trying to do something I think is pretty basic.  I want to run a nightly batch that will summarize all of the Closed Won Opportunites by Account.  (Forget the fact that these roll-up by default.  I'm actually doing something different enough where this won't work.)  We have tons of Opportunities and I need to do this in a nightly batch file.  I'm comfortable with batches cranking away on Opportunities, but how would I keep a running tab BY ACCOUNT given that a specific batch might not have all of the Opportunities associated with that Account?

I'm trying to do something I think is pretty basic.  I want to run a nightly batch that will summarize all of the Closed Won Opportunites by Account.  (Forget the fact that these roll-up by default.  I'm actually doing something different enough where this won't work.)  We have tons of Opportunities and I need to do this in a nightly batch file.  I'm comfortable with batches cranking away on Opportunities, but how would I keep a running tab BY ACCOUNT given that a specific batch might not have all of the Opportunities associated with that Account?