Transcription of Exercises - web.cs.ucla.edu
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Exercises9personownscarparticipatedaccid entaddressdamage-amountmodelyearlicensen amereport-numberdatelocationdriver-iddri verFigure for a Car-insurance the distinctions among the terms primary key, candidate key, and :Asuperkeyis a set of one or more attributesthat, taken collectively, al-lows us to identify uniquelyan entityin the entity set. A superkeymay containextraneous attributes. IfKis a superkey, then so is any no proper subsetis also a superkeyis called that severaldistinct sets of attributescould serve as candidatekeys. Theprimary keyis one of the candidate keys that is chosen by the database designeras the principal means of identifying entitieswithin an entity anE-Rdiagram for a car-insurance company whose customers ownone or more cars each. Eachcar has associated with it zero to any number ofrecorded :See Figure anE-Rdiagram for a hospital with a set of patients and a set of medi-cal doctors.
r-number capacity building exam-id Figure 2.12 E-R diagram for exam scheduling. 2.15 When designing an E-R diagram for a particular enterprise, you have several alternatives from which to choose. a. What criteria should you consider in making the appropriate choice? b. Design three alternative E-R diagrams to represent the university registrar™s
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