1-introduction-to-database.

2021/3/28DatabaseSystem1IntroductiontoDatabases—Chapter1—[e-mail]2021/3/28DatabaseSystem2ObjectivesSomecommonusesofdatabasesystems.Characteristicsoffile-basedsystems.Problemswithfile-basedapproach.Meaningofthetermdatabase.MeaningofthetermDatabaseManagementSystem(DBMS).2021/3/28DatabaseSystem3ObjectivesTypicalfunctionsofaDBMS.MajorcomponentsoftheDBMSenvironment.PersonnelinvolvedintheDBMSenvironment.HistoryofthedevelopmentofDBMSs.AdvantagesanddisadvantagesofDBMSs.2021/3/28DatabaseSystem4AgendaExamplesofDatabaseApplicationsFile-basedSystemsDatabaseApproachDatabaseUsersHistoryofDatabaseSystemsAdvantagesandDisadvantagesofDBMSSimpleStructureofaDBMS2021/3/28DatabaseSystem5ExamplesofDatabaseApplicationsPurchasesfromthesupermarketPurchasesusingyourcreditcardBookingaholidayatthetravelagentsUsingthelocallibraryTakingoutinsuranceUsingtheInternetStudyingatuniversity2021/3/28DatabaseSystem6DiscussionIdentifysomefurtherexamplesofdatabasesystems2021/3/28DatabaseSystem7AgendaExamplesofDatabaseApplicationsFile-basedSystemsDatabaseApproachDatabaseUsersHistoryofDatabaseSystemsAdvantagesandDisadvantagesofDBMSSimpleStructureofaDBMS2021/3/28DatabaseSystem8File-basedSystemsCollectionofapplicationprogramsthatperformservicesfortheendusers(e.g.reports).Eachprogramdefinesandmanagesitsowndata.2021/3/28DatabaseSystem9File-basedProcessing2021/3/28DatabaseSystem10LimitationsofFile-basedApproachSeparationandisolationofdataEachprogrammaintainsitsownsetofdata.Usersofoneprogrammaybeunawareofpotentiallyusefuldataheldbyotherprograms.DuplicationofdataSamedataisheldbydifferentprograms.Wastedspaceandpotentiallydifferentvaluesand/ordifferentformatsforthesameitem.2021/3/28DatabaseSystem11LimitationsofFile-basedApproachDatadependenceFilestructureisdefinedintheprogramcode.IncompatiblefileformatsProgramsarewrittenindifferentlanguages,andsocannoteasilyaccesseachothersfiles.FixedQueries/ProliferationofapplicationprogramsProgramsarewrittentosatisfyparticularfunctions.Anynewrequirementneedsanewprogram.2021/3/28DatabaseSystem12QuestionDescribetheapproachtakentothehandlingofdataintheearlyfile-basedsystems.Discussthedisadvantagesofthisapproach.2021/3/28DatabaseSystem13AgendaExamplesofDatabaseApplicationsFile-basedSystemsDatabaseApproachDatabaseUsersHistoryofDatabaseSystemsAdvantagesandDisadvantagesofDBMSSimpleStructureofaDBMS2021/3/28DatabaseSystem14DatabaseApproachArosebecause:Definitionofdatawasembeddedinapplicationprograms,ratherthanbeingstoredseparatelyandindependently.Nocontroloveraccessandmanipulationofdatabeyondthatimposedbyapplicationprograms.ResultthedatabaseandDatabaseManagementSystem(DBMS).2021/3/28DatabaseSystem15DatabaseSharedcollectionoflogicallyrelateddata,andadescriptionofthisdata,designedtomeettheinformationneedsofanorganization.Systemcatalog(metadata)providesdescriptionofdatatoenableprogram–dataindependence.Logicallyrelateddatacomprisesentities,attributes,andrelationshipsofanorganization'sinformation.Entities:adistinctobjectintheorganizationAttributes:asomeaspectpropertyoftheobjectRelationships:anassociationbetweenentities.2021/3/28DatabaseSystem16DatabaseAdvantageofthisapproachDataabstractionseparatesthestructureofthedatafromtheapplicationprogramsandstoresitinthedatabase.Ifnewdatastructureareaddedorexistingstructuresaremodifiedthentheapplicationprogramsareunaffected,providedtheydonotdirectlydependuponwhathasbeenmodified.2021/3/28DatabaseSystem17DatabaseManagementSystem(DBMS)DBMSAsoftwaresystemthatenablesuserstodefine,create,andmaintainthedatabaseandwhichprovidescontrolledaccesstothisdatabase.2021/3/28DatabaseSystem18DBMS-FunctionsDatadefinitionlanguage(DDL).Permitsspecificationofdatatypes,structuresandanydataconstraints.Allspecificationsarestoredinthedatabase.Datamanipulationlanguage(DML).Generalenquiryfacility(querylanguage)ofthedata.2021/3/28DatabaseSystem19DBMS-FunctionsControlledaccesstodatabasemayinclude:Asecuritysystem.Anintegritysystem.Aconcurrencycontrolsystem.Arecoverycontrolsystem.Auser-accessiblecatalog.2021/3/28DatabaseSystem20DatabaseApplicationProgramsacomputerprogramthatinteractswithdatabasebyissuinganappropriaterequest(SQLstatement)totheDBMS.CanbeconventionalbatchapplicationsoronlineapplicationsTheapplicationprogramsmaybewritteninsomeprogramminglanguageorinsomehigher-levellanguage.2021/3/28DatabaseSystem21DatabaseSystemAsoftwaresystemtostore,access,modify,manageandmanipulatedatatosupporttheoperationsofaspecificorganizationoraspecificsetofapplicationsIncludes:AnapplicationspecificdatabaseADBMSthatmaintainsthedatabaseTheapplicationprogramthatmanipulatesthedatabase2021/3/28DatabaseSystem22DatabaseProcessingFourelementsUserAnapplicationspecificdatabaseDBMS:maintainsthedatabaseTheapplicationprogram:manipulatesthedatabaseandfinishesenterprisetransactions2021/3/28DatabaseSystem23DatabaseProcessing2021/3/28DatabaseSystem24QuestionDescribethemaincharacteristicsofthedatabaseapproachandcontrast