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1、DatabaseSystems:TheCompleteBookSolutionsforChapter2SolutionsforSection2.1Exercise2.1.1TheE/RDiagram.Exercise2.1.8(a)TheE/RDiagramKobvxybzSolutionsforSection2.2Exercise2.2.1TheAddressesentitysetisnothingbutasingleaddress,sowewouldprefertomakeaddressanattribut
2、eofCustomers.Werethebanktorecordseveraladdressesforacustomer,thenitmightmakesensetohaveanAddressesentitysetandmakeLives-atamany-manyrelationship.TheAcct-Setsentitysetisuseless.Eachcustomerhasauniqueaccountsetcontaininghisorheraccounts.However,relatingcustome
3、rsdirectlytotheiraccountsinamany-manyrelationshipconveysthesameinformationandeliminatestheaccount-setconceptaltogether.SolutionsforSection2.3Exercise2.3.1(a)KeysssNoandnumberareappropriateforCustomersandAccounts,respectively.Also,wethinkitdoesnotmakesensefor
4、anaccounttoberelatedtozerocustomers,soweshouldroundtheedgeconnectingOwnstoCustomers.Itdoesnotseeminappropriatetohaveacustomerwith0accounts;theymightbeaborrower,forexample,soweputnoconstraintontheconnectionfromOwnstoAccounts.HereistheTheE/RDiagram，showingunde
5、rlinedkeysandthenumerocityconstraint.Exercise2.3.2(b)IfRismany-onefromE1toE2,thentwotuples(e1,e2)and(f1,f2)oftherelationshipsetforRmustbethesameiftheyagreeonthekeyattributesforE1.Toseewhy,surelye1andf1arethesame.BecauseRismany-onefromE1toE2,e2andf2mustalsobe
6、thesame.Thus,thepairsarethesame.SolutionsforSection2.4Exercise2.4.1HereistheTheE/RDiagram.WehaveomittedattributesotherthanourchoiceforthekeyattributesofStudentsandCourses.Alsoomittedarenamesfortherelationships.AttributegradeisnotpartofthekeyforEnrollments.Th
7、ekeyforEnrollementsisstudIDfromStudentsanddeptandnumberfromCourses.Exercise2.4.4bHereistheTheE/RDiagramAgain,wehaveomittedrelationshipnamesandattributesotherthanourchoiceforthekeyattributes.ThekeyforLeaguesisitsownname;thisentitysetisnotweak.ThekeyforTeamsis
8、itsownnameplusthenameoftheleagueofwhichtheteamisapart,e.g.,(Rangers,MLB)or(Rangers,NHL).ThekeyforPlayersconsistsoftheplayer'snumberandthekeyfortheteamonwhichheorsheplays.Sincethelatterkeyisitsel
