For such scenarios Views are usually the best choice.

>Hi,
>
>I am looking for suggestions of better practice when using or not using a Calculated field. Let me describe on an example what I mean by Calculated field (perhaps this is not quite the right term).
>
>Purchase Order and Invoice System. There is a P.O. table (vendor, date, amount, etc.). and P.O. Invoice table. Invoice table is a child table where there could be several records for each P.O. Each P.O. Invoice record has Freight and Sales Tax amount. I need to show on the P.O. Master view the total amount of Freight and Sales tax paid against the P.O. So one approach is to add fields FREIGHT and SALES_TAX to the P.O. Master table and update it on every entry in the Invoice posting. Another approach is to NOT to have these fields in the P.O. Master table but to calculate the total amount on-the-fly. That is, call a method/function that gets all invoices of the P.O. and calculates the total amounts.
>
>Which of the two approaches is better practice, in your opinion. TIA.