FlowField and SumIndexField functions

In Chapter 3, Data Types and Fields, we discussed SumIndexFields and FlowFields in the context of table, field, and key definition. To recap briefly, SumIndexFields are defined in the screen where table keys are defined. They allow very rapid calculation of values in filtered data. In most ERP and accounting software systems, the calculation of group totals, periodic totals, and such, require reading of all the data to be totaled.

SIFT allows a NAV system to respond almost instantly with totals in any area where the SumIndexField was defined and is maintained. In fact, use of SIFT totals combined with NAV's retention of detailed data supports totally flexible ad hoc queries in similar form to: "What were our sales for red widgets between the dates of November 15th and December 24th?" And the answer is returned almost instantly! SumIndexFields are the basis of FlowFields which have a Method of Sum or Average; such a FlowField must...