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1、ComputingEssentials2008Chapter12:Databases·Data(340)oFactsorobservationsaboutpeople,places,things,andevents.oTypesofdata§Numbers,letters,andsymbolsrecordedbykeyboards.§Audiocaptured,interpreted,andsavedusingmicrophonesandvoicerecognitionsystems§Musiccapt
2、uredfromtheInternet,fromMIDIdevices,andfromothersources.§Photographscapturedbydigitalcameras,andeditedbyimageeditingsoftware.§Videocapturedbydigitalvideocameras,TVtunercards,andWebCams.oPhysicalviewfocusesontheactualformatandlocationofthedataoLogicalview
3、,focusesonthemeaningandcontentofthedata.·DataOrganization(340)oCharacter-themostbasiclogicaldataelement.oField-groupofrelatedcharacters.oRecord-acollectionofrelatedfields.oFile-acollectionofrelatedrecords.oDatabase-anintegratedcollectionoflogicallyrelate
4、drecordsorobjects.oKeyField(341)§Eachrecordinadatabasehasatleastonedistinctivefield§Thisfielduniquelyidentifiestherecord.§Keyfieldsindifferentfilescanbeusedtointegratethedatainadatabase.oBatchvs.Real-timeprocessing§Batch·Dataiscollectedoverseveralhours,d
5、ays,orevenweeks,thenprocessedallatonce§Real-time·Alsoknownasonlineprocessing·Occurswhendataisprocessedatthesametimethetransactionoccurs.·Database(343)oManyorganizationshavemultiplefilesonthesamesubjectorperson.oDataspreadaroundindifferentfilesisnotasusef
6、ul.oNeedfordatabases§Sharing-informationfromonedepartmentcanbereadilysharedwithothers.§Security-Usersaregivenpasswordsoraccessonlytothekindofinformationtheyneed.§Lessdataredundancy-havingaccesstoonefile,therearefewerfiles.Thus,storageisreduced.§Datainteg
7、rity-achangemadetoafilebyonedepartmentwillbeseenbyotherdepartments.Accuracyisimproved.oDatabaseManagement(344)§Allowsuserstocreate,modify,andgainaccesstoadatabase,specialsoftwareisrequired.ChapterOutlinePage4of12ComputingEssentials2008Chapter12:Databases
8、§TheDBMSengineprovidesabridgebetweenthelogicalviewofthedataandthephysicalviewofthedata.§Thedatadefinitionsubsystemdefinesthelogicalstructureofthedatabasebyusingadatadictionary.§Thedatamanipulationsubsystemprovidestoolsform
