
If the meaning of each entity and relationship type is kept clearly in mind, most
decisions on attribute assignment will be perfectly straightforward. The rules proposed
here are an aid to commonsense, not a substitute.
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Suppose the attributes employeeName, make, carTotalMiles, currentMiles, and
employeeTotalMiles are to be added to the skeleton tables defined in section 12.2 for
various 1:1 relationships between Employee and Car. An employee has only one
employeeName, and a car is of only one make. The attribute carTotalMiles is the
cumulative mileage recorded on a car’s mileometer; currentMiles is the mileage
travelled by an employee ...