ch1-additional info - 2012-spring (1)

©Silberschatz,KorthandSudarshan1.1DatabaseSystemConcepts-5thEdition,May23,2005PrinciplesofdatabasesystemsTextbook:DatabaseSystemConcepts(5thEdition)Instructor:SUNJianling(孙建伶)(Professor)Office:Yi-FuGongShangBuilding234(逸夫工商管理楼234)YuQuanCampus(玉泉校区)Email:[e-mail]:87952700(O),13705818519(M)CourseTA:LIUChenghao(刘成昊)(PhDcandidate)Email:[e-mail]:13738194665©Silberschatz,KorthandSudarshan1.2DatabaseSystemConcepts-5thEdition,May23,2005PrinciplesofdatabasesystemsCourseGradingPolicy:Exercises&Quiz15%Lab&Project30%FinalExam55%(opentwo-pagenote)CourseURL:()验证码：2975©Silberschatz,KorthandSudarshan1.3DatabaseSystemConcepts-5thEdition,May23,2005DatabaseinComputerScienceAI、CAD&CG、Multimedia、e-commerence、NumericalAnalysis、SoftwareEngine、EmbeddedSystemC、C++、Java、DataStructure,AlgorithmComplier、Database、NetworkOperatingSystemComputerOrganization、ComputerArchitecture、AssembleCircuit,Digitalcircuit©Silberschatz,KorthandSudarshan1.5DatabaseSystemConcepts-5thEdition,May23,2005Chapter1:IntroductionPurposeofDatabaseSystemsViewofDataDatabaseLanguagesRelationalDatabasesDatabaseDesignObject-basedandsemistructureddatabasesDataStorageandQueryingTransactionManagementDatabaseArchitectureDatabaseUsersandAdministratorsOverallStructureHistoryofDatabaseSystems©Silberschatz,KorthandSudarshan1.6DatabaseSystemConcepts-5thEdition,May23,2005DatabaseManagementSystem(DBMS)DBMScontainsinformationaboutaparticularenterpriseCollectionofinterrelateddataSetofprogramstoaccessthedataAnenvironmentthatisbothconvenientandefficienttouseDatabaseApplications(数据库应用系统):Banking:alltransactionsAirlines:reservations,schedulesUniversities:registration,gradesSales:customers,products,purchasesOnlineretailers:ordertracking,customizedrecommendationsManufacturing:production,inventory,orders,supplychainHumanresources:employeerecords,salaries,taxdeductionsDatabasestouchallaspectsofourlives!©Silberschatz,KorthandSudarshan1.7DatabaseSystemConcepts-5thEdition,May23,2005PurposeofDatabaseSystemsIntheearlydays,databaseapplicationswerebuiltdirectlyontopoffilesystemsDrawbacksofusingfilesystemstostoredata:Dataredundancy(数据冗余)andinconsistency(不一致性)Multiplefileformats,duplicationofinformationindifferentfilesDataisolation(数据孤立)—multiplefilesandformatsDifficultyinaccessingdata(存取数据困难)NeedtowriteanewprogramtocarryouteachnewtaskIntegrityproblems(完整性问题)Integrityconstraints(e.g.accountbalance0)become“buried”inprogramcoderatherthanbeingstatedexplicitlyHardtoaddnewconstraintsorchangeexistingones©Silberschatz,KorthandSudarshan1.8DatabaseSystemConcepts-5thEdition,May23,2005PurposeofDatabaseSystems(Cont.)Drawbacksofusingfilesystems(cont.)Atomicityofupdates(Recovery)(更新的原子性,恢复)FailuresmayleavedatabaseinaninconsistentstatewithpartialupdatescarriedoutExample:TransferoffundsfromoneaccounttoanothershouldeithercompleteornothappenatallConcurrentaccess(并发存取)bymultipleusersConcurrentaccessedneededforperformanceUncontrolledconcurrentaccessescanleadtoinconsistencies–Example:TwopeoplereadingabalanceandupdatingitatthesametimeSecurityproblems(安全问题)Hardtoprovideuseraccesstosome,butnotall,dataDatabasesystemsoffersolutionstoalltheaboveproblems©Silberschatz,KorthandSudarshan1.9DatabaseSystemConcepts-5thEdition,May23,2005ViewofDataAnarchitectureforadatabasesystemview/logicalmappinglogical/physicalmapping©Silberschatz,KorthandSudarshan1.10DatabaseSystemConcepts-5thEdition,May23,2005ViewofDataPhysicallevel(物理层):describeshowarecord(e.g.,customer)isstored.Logicallevel(逻辑层):describesdatastoredindatabase,andtherelationshipsamongthedata.typecustomer=recordcustomer_id:string;customer_name:string;customer_street:string;customer_city:integer;end;Viewlevel(视图层):applicationprogramshidedetailsofdatatypes.Viewscanalsohideinformation(suchasanemployee’ssalary)forsecuritypurposes.©Silberschatz,KorthandSudarshan1.11DatabaseSystemConcepts-5thEdition,May23,2005InstancesandSchemas(实例和模式)SimilartotypesandvariablesinprogramminglanguagesSchema(模式)–thelogicalstructureofthedatabaseExample:Thedatabaseconsistsofinformationaboutasetofcustomersandaccountsandtherelationshipbetweenthem)AnalogoustotypeinformationofavariableinaprogramPhysicalschema(物理模式):databasedesignatthephysicallevelLogicalschema(逻辑模式):databasedesignatthelogicallevelInstance(实例)–theactualcontentofthedatabaseataparticularpointintimeAnalogoustothevalueofavariablePhysicalDataIndependence(物理数据独立性)–theabilitytomodifythephysicalschemawithoutchangingthelogicalschemaApplicationsdependonthelogicalschemaIngeneral,theinterfacesbetweenthevariouslevelsandcomponentsshouldbewelldefinedsothatchangesinsomepartsdonotseriouslyinfluenceothers.LogicalDataIndependence(逻辑数据独立性)–theabilitytomodifythelogicalschemawithoutchangingtheuserviewschema©Silberschatz,KorthandSudarshan1.12DatabaseSystemConcepts-5thEdition,May23,2005DataModels(数据模型)AcollectionoftoolsfordescribingData(数据)Datarelationships(联系)Datasemantics(语义)Datacon