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1、DatabasesystemIntroductionWhatisDatabaseSystems?PurposeofDatabaseSystemsDataAbstractionDatabaseLanguagesDatabaseUsersDatabaseSystemStructureApplicationArchitecturesHistoryofDatabaseSystemsDatabaseSystemDatabaseSystemDatabaseDBMSDatabase:Collectionofinterrelateddata(informationab
2、outaparticularenterprise)Largeamountofinformation(data)Wellorganized:DefinitionandManipulationShareamongseveralusers,avoidpossibleanomalousresultsSafetyoftheinformationstored,despitesystemcrashorunauthorizedaccessDBMSisasoftware:SetofprogramstoaccessthedataBeabletomanagedatabase
3、s.Providesanenvironmentthatisbothconvenientandefficienttouse.DatabaseApplicationsDatabasetouchallaspectsofourlivesBanking:alltransactionsAirlines:reservations,schedulesUniversities:registration,gradesSales:customers,products,purchasesManufacturing:production,inventory,orders,sup
4、plychainHumanresources:employeerecords,salaries,taxdeductionsUseofdatabasegrewlastfourdecadesVeryfewpeopleinteracteddirectlywithdatabasesystem,customdidnotknowthebackenddatabase,theygotprintedreport,etc.Somecustomsaccesssystemviaphoneinterface.DirectuseraccessviaInternet.Thepurp
5、oseofthecourseistounderstandthefundamentalofDatabaseSystem.HowtouseDBMS.(included)HowDBMSworks.(Abriefintroduction)PurposeofDatabaseSystemsIntheearlydays,databaseapplicationswerebuiltontopoffilesystemsDrawbacksofusingfilesystemstostoredata:DataredundancyandinconsistencyMultiplef
6、ileformats,duplicationofinformationindifferentfilesDifficultyinaccessingdataNeedtowriteanewprogramtocarryouteachnewtaskDataisolation—multiplefilesandformatsIntegrityproblemsIntegrityconstraints(e.g.accountbalance>0)becomepartofprogramcodeHardtoaddnewconstraintsorchangeexistingon
7、esPurposeofDatabaseSystems(Cont.)Drawbacksofusingfilesystems(cont.)AtomicityofupdatesFailuresmayleavedatabaseinaninconsistentstatewithpartialupdatescarriedoutE.g.transferoffundsfromoneaccounttoanothershouldeithercompleteornothappenatallConcurrentaccessbymultipleusersConcurrentac
8、cessedneededforperformanceUncontrolledconcurren
