2. Data redundancy exists when unnecessarily duplicated data are found in the database. For example, a
customer's telephone number may be found in the customer file, in the sales agent file, and in the
invoice file. Data redundancy is symptomatic of a (computer) file system, given its inability to represent
and manage data relationships. Data redundancy may also be the result of poorly-designed databases
that allow the same data to be kept in different locations. (Here's another opportunity to emphasize the
need for good database design!)
(See Section 1.6.2, Data Redundancy.)