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.