Introducing Microsoft® Office InfoPath™ 2003

Displaying Running Sums in an Expression Box

One of the fundamental rules of database design is to eliminate storing in tables duplicate data or information that’s calculated from database column values. Using the NorthwindCS database as an example, storing the extended net amount of an Order Details record in an Extended column requires updating the Extended value whenever the Quantity or Discount values change. Similarly, storing the sum of Extended values as the total order amount—less freight, taxes, and other charges—requires recalculating this value each time an Extended value changes or line items are added to or deleted from the order. The most common practice is to create views or stored procedures that provide calculated values. Views ...