What is a derived attribute? Give an example.
A derived attribute is an attribute whose value is calculated (derived) from other attributes. The
derived attribute need not be physically stored within the database; instead, it can be derived by using
an algorithm. For example, an employee’s age, EMP_AGE, may be found by computing the integer
value of the difference between the current date and the EMP_DOB. If you use MS Access, you would
use INT((DATE() – EMP_DOB)/365).
Similarly, a sales clerk's total gross pay may be computed by adding a computed sales commission to
base pay. For instance, if the sales clerk's commission is 1%, the gross pay may be computed by
EMP_GROSSPAY = INV_SALES*1.01 + EMP_BASEPAY
Or the invoice line item amount may be calculated by
LINE_TOTAL = LINE_UNITS*PROD_PRICE