A derived attribute is normally deleted from the E-R diagram, since its
value can, by definition, be derived from the value of other attributes
and its presence would therefore represent a redundancy.
Exercise:
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Delete the derived attribute.
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Click at compare with solution to verify your result
If the redundancy is needed, say, for performance reasons, then the
derived attribute is left in the diagram and treated just like any other
attributes. If it is removed, a note may be included in the functional
requirements list as a reminder, that a calculated valued is needed.