Topic group Related topics

Using multiple tables reduces redundant information. In addition, don’t store information that you can easily calculate, unless the calculation requires excessive processing effort or you need an audit trail. For example, if you were creating tables for our hypothetical dive shop, you might want to store the total invoice amount, but not the total sales tax, which dBASE Plus can easily calculate.

In general, indexed fields that are used for linking should be the only fields that contain redundant information in related tables. Identical data in index fields is necessary for linking tables. In this example, it is the way to identify the same customer in both tables.