If you're not doing any other summation or grouping, I'm not sure you'll find anything more efficient than the straight 'select' in my question. It would only touch the absolute total row once and the cumulative math has to be done somewhere. If there is other summation required, I'd have to know what that was in order to give you a solution.

The more advanced folks here may be able to give you a better solution, so I'll sit back and wait to (once again) learn something.