[数据库原理]【英文版】chapter13

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1、Chapter13-Objectives©Thepurposeofnormalization.©Hownormalizationcanbeusedwhendesigningarelationaldatabase.©ThepotentialproblemsassociatedwithredundantdataChapter13inbaserelations.©Theconceptoffunctionaldependency,whichdescribestherelationshipbetweenattributes.Normalization©Thecharacteristicsoffunct

2、ionaldependenciesusedinnormalization.©Howtoidentifyfunctionaldependenciesforagivenrelation.©Howfunctionaldependenciesidentifytheprimarykeyforarelation.2Chapter13-ObjectivesPurposeofNormalization©Normalizationisatechniqueforproducingasetofsuitablerelations©Howtoundertaketheprocessofnormalization.tha

3、tsupportthedatarequirementsofanenterprise.©Mainobjectiveindevelopingalogicaldatamodelforrelational©Hownormalizationusesfunctionaldependenciestodatabasesystemsistocreateanaccuraterepresentationofthedata,itsgroupattributesintorelationsthatareinaknownrelationships,andconstraints.©Characteristicsofasui

4、tablesetofrelationsinclude:normalform.–theminimalnumberofattributesnecessarytosupportthedata©Howtoidentifythemostcommonlyusednormalrequirementsoftheenterprise;forms,namelyFirstNormalForm(1NF),Second–attributeswithacloselogicalrelationshiparefoundinthesamerelation;NormalForm(2NF),ThirdNormalForm(3NF

5、),and–minimalredundancywitheachattributerepresentedonlyonceBoyce–CoddNormalForm(BCNF).withtheimportantexceptionofattributesthatformallorpartofforeignkeys.©HowtoidentifyFourthNormalForm(4NF)andFifth©ThebenefitsofusingadatabasethathasasuitablesetofrelationsisNormalForm(5NF).thatthedatabasewillbe:–eas

6、ierfortheusertoaccessandmaintainthedata;–takeupminimalstoragespaceonthecomputer.341HowNormalizationSupportsDatabaseDesignNormalization©Fourmostcommonlyusednormalformsarefirst(1NF),second(2NF)andthird(3NF)normalforms,andBoyce–Coddnormalform(BCNF).©Basedonfunctionaldependenciesamongtheattributesofare

7、lation.©Arelationcanbenormalizedtoaspecificformtopreventpossibleoccurrenceofupdateanomalies.56DataRedundancyandUpdateAnomaliesDataRedundancyandUpdateAnomalies©Majoraimofrelationaldatabasedesignistogroupattr