...there is no reason to store a "calculated" field in a table. That's why they invented queries. When you need a calculation done on fields in a record or table, a query does that. Then DISPLAY the results on your form or report.
That is what all the books say also. And as I mentioned before, this particular thread is a poor example of needing to store a calculated field. However, a real life example from a current DB I am working on is for our Marine Dealership to control inventory of all the used boats that come in on trade. The boat is not the only thing to be inventoried. Usually there is a packaged cost of boat, motor and trailer. TO determine cost, we get the value of the 3 pieces individually and combine them into a package deal. Then any additional costs have to be added (such as prep, paint, repairs, trade in allowance, etc.) and added to the package total. This gives a total cost. Now to determine a list value, we have to determine certain multipliers (i.e. condition of boat, amount of time boat is stored, associated costs for maintenance, etc). Also, for convenience, it would be nice to factor in a high and low percentage for special sales and promotions. THis is hard to perform all the calculations needed for the "Cost" feild without storing the value of the cost. This total would be added in a query based on trailer, boat and motor costs. The result would be the displayed value of the query. You wouldn't want to recalculate the individual costs, and add any additional multipiers to the query total each time, would you??? Soon you would be dealing with endless queries to calculate input values for more queries. Where as a stored cost value would allow easier calculations. Also, for year end totals, reports, etc, this would seem the most logical approach (to pass the value of the query to a field). Am I correct in my assumptions, or am I missing something? I am relatively new to Access, and may have a fundamental flaw in my design approaches. I am not trying to be argumentative or win my point, I am truly currious as to the best approach to design proper DB's. Is there a simpler or more idealogical approach to this particular DB? Many of the Databases I am working with involve inventory and quantity tracking, as well as statistical analysis of inventory, so this is going to be a reoccuring problem. If there is a better approach, let me know.