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Relational database management system



Basicinformation

RelationalDatabaseManagementSystem(RDBMS)referstoasetofprocedures(databasemanagementsystemsoftware)thatincludesinterconnectedlogicalorganizationsandaccesstothesedata.Arelationaldatabasemanagementsystemisasystemthatmanagesrelationaldatabasesandlogicallyorganizesdata.

ThecommonlyusedrelationaldatabasemanagementsystemproductsareOracle,IBM'sDB2andMicrosoft'sSQLServer.

Designprocess

Databasedesignoccupiesaveryimportantpositioninsystemdevelopment.Thequalityofdatabasedesigndirectlyaffectstheentiresystem.

Thecoreofdatabasedesignisdatamodeling,whichistoestablishadatamodeloftherealdataworldforthedevelopmentofanapplicationsystem.Thegoalofdatabasedesignistobuildadatabasethatislessredundant,easytomaintain,andeasytouse.Easymaintenanceincludesnoabnormaloperationofvariousoperations,andthesecurity,consistency,andintegrityofthedatabasearealsoguaranteed;easeofuseincludeshighaccessefficiencyinadditiontoconvenientuse.

Generallyspeaking,thedatabasedesignprocesscanbedividedintothreestages,namelyconceptualdesign,logicaldesignandphysicaldesign.

Conceptualdesign

Conceptualdesignistoanalyzetheuser'sbusinessactivities,understandtheuser'suseofthedatabase,anddeterminetheuser'srequirementsfortheuseofthedatabaseandtherequirementsfortheintegrityofthedatabase.

Theconceptualdesignstagecanbedividedintothreesteps,thatis,analyzingtheentireuserenvironment,determiningthesystemboundaryandanalyzingtheinternalstructureofthesystem.

1.Analyzingtheentireuserenvironmentmeansunderstandingtheuser’sbusinessactivitiesfromtheperspectiveofdataprocessing.Tothisend,datacollectionandcorrespondinginvestigationsmustbecarriedoutfirst.Thecontentsofthesurveymainlyinclude:

(1)Thecurrentbusinessprocesswithintheorganization,andvariousdatareflectingthebusinessprocess,suchasbills,files,contracts,plansandreports,etc.

(2)Dataelementsanddataflow.Fordataelements,itisnecessarytoinvestigatethenatureofthevariousdata,thevaluerange,theprovidingdepartment,theusingdepartment,thecontrolauthority,theconfidentialityrequirement,thefrequencyofuse,andtherelationshipbetweenthedata.Thedataflowreflectsthesituationofdataprocessingactivities,includingtherelationshipbetweenthedataprovidingdepartment,theprocessingdepartmentandthedatausingdepartment.

(3)Theamountofdata.Whicharebasicdataandwhichareintermediatedata.

(4)Theuser'sdatarequirementsandprocessingrequirementsforthecomputer,theoutputdataandoutputdata,therequiredreportform,etc.

Duetothelimitationsoftheprofessionalknowledgeofusersanddesigners,itisbestforusersanddesignerstoanalyzeandunderstandtheneedsofuserstogether.Atleastthedatabasedesignerisrequiredtocommunicatewithusersasmuchaspossibleandfullyunderstandtheprocessingrequirementsofusers.Thisworkisgenerallyrepeatedmanytimes.Finally,thedesignerdrawsauseractivitydiagrambasedontheuser'sdataprocessingactivitiesandobtainstheuser'spermission.Onthebasisofinvestigationandanalysis,togetherwithusers,arequirementanalysisspecificationdocumentisformed,whichservesastheinspectionstandardforthefinaldesign.

2.Determiningthesystemboundaryistodeterminethescopeofthecomputersystemanditsrelationshipwiththeexternalenvironmentonthebasisofinvestigatingthestatusquoofinformationprocessing.Inthisstep,itisnecessarytodecidewhichprocessingactivitiesarecompletedbythesystemandwhicharestillcompletedmanually.Accordingtothesystemenvironmentandconditions,thesystemfunctionsareproposed.

3.Analyzetheinternalstructureofthesystem.Thatis,tofindoutallthedatarequirementsandprocessingrequirementsandtheirinterrelationships.Forthedata,itisnecessarytoidentifyallthedataitemsandtheirdependencies,andfortheprocessing,itisnecessarytounderstandalltheprocessingprocessesandtheirinputandoutputdata.Duetothecomplexityofthispartofthework,ahierarchicaldecompositionmethodcanbeusedtodecomposethedataprocessingprocessoftheentiresystemintoseveralsmallsub-processes,andthenthesub-processesaredecomposedintosmallerprocessingprocessesuntilitiseasytoanalyze.Eachsub-processingprocessshouldberelativelyindependent,relativelysimpletocommunicatewitheachother,withclearfunctionsandclearinterfaces.Itcanberepresentedbyadataflowdiagram.

Next,wewilldothesecondpieceofanalysiswork,thatis,analyzethedataandtherelationshipbetweenthedata,andanalyzetheirrelationshipfromthesmallestdataunit-thedataitem.

Thelogicaldesignofthedatabase

Thelogicaldesignofthedatabaseistodeterminethelogicalstructureoftheentiredatabaseaccordingtotherequirementsanddesigntheoryofthedatabase,thatis,todeterminewhichrelationships(files)consistoftheentiredatabase.Whatattributesaremadeupofeachrelationship,andsoon.

Accordingtotheresultsofthedemandanalysis,wealreadyknowthedataitemsinthesystemandtheirdependencies(connectionsbetweendata).Atthistime,E-RdiagramsandSmithdiagrams(dependencydiagrams)canbeused.)Tocompletethelogicaldesigntaskofthedatabase.

Thephysicaldesignofthedatabase

Thetaskofthephysicaldesignofthedatabaseistomakethelogicalstructureofthedatabasetoberealizedontheactualphysicalequipment,andtousetheexistingphysicalstorageequipmenttoeffectivelystoreStoredata,thatis,determinetheactualaccessmethodandotherdetailsofthedatabase.ThisstepdiffersdependingontheDBMSsystem,andsomeareverycomplex(suchashierarchical,network-basedDBMS),butforrelationalDBMS,thisstepisrelativelysimple.Forexample,fortheFoxBASEsystem,thephysicaldesignprocessgenerallyincludes:determiningthetypeandlengthofeachfield,selectingthefieldtobeindexed,etc.,andotherphysicaldesigntasksareautomaticallycompletedbythesystem,andthedesignerdoesnothavetoworryaboutit.

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