>Of course, some developers will take the route of breaking normal form, and will store the pay rate for the day on each timesheet row, at the time the timesheet row is inserted.

Kevin,

I would disagree with you that storing the rate in the timesheet table is necessarily a violation of normal form as the rate in the timesheet table has a different domain definition than the rate in the rates table. The rate in the rates table is the rate for a given calendar period, while the rate in the timesheet table is the rate at which this specific timesheet entry was paid (there may be a variety of reasons why the timesheet has a different rate than the rate table would indicate). I would, in fact, say that the very problem you describe indicates that the rate needs to be in the timesheet table or else there is a missed recording of that attribute domain.

This is very similar to the tax rate issue where you have a tax rate table and you need to decide whether or not you will store the tax rate in the invoice data. I interpret that the tax rate must be recorded in the invoice data as there can be a difference between the given tax rate in the tax rate structure and the rate of taxation for a specific invoice. The recording of tax rate in the invoice data structure here is NOT a violation of normal form, it is, in fact, necessary for complete data recording.