Saving results of complex MySQL query/report

I'm looking for the best way to implement the following.

I have a MySQL query that analyses performance of a company, and outputs sales, revenue, costs and so on, and basically outputs a final Gross Profit and Net Profit figure. It's working well, and managers can select any date range to run it for, and it will output everything for that range - therefore they can in theory see how the company performed today, yesterday, this week, last month or on the 17th of three months ago... you get the point.

There comes a problem however when some of the figures to be used for the report are variable, and involve fluctuating external costs, such as overheads and so on. I allow users to specify these costs and ov开发者_如何学Cerheads in a settings table, and the performance query uses these to calculate it's figures. But these variable figures represent now, so would bear no relevance if you wanted to look at the company performance from X months/years in the past, when the overheads for today are being offset against them, creating inaccuracy.

I thought of a couple of solutions.

1. I could allow the managers to set a date range to apply the overheads for. For example, for June 2011, the daily overhead was £2000, whereas in July 2011 the overhead is £2250.
2. Or I could save the performance report/query to another table, which would obviously have the variable figure locked in from the time it ran. This could even be automated with a crontab, and perhaps just ran every night.

Which way would you recommend?

If I were you I would go with the first option (1), and create a table to store the delayed overheads for a specific date. This would be much more flexible for you to run any kind of query at any point on time against the pure/"virgin" data you have on the table.

On the other hand the second option doesn't seem that feasible to me, because you can't possibly calculate all the complexity of the queries and reports needed, in different date ranges.