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1、数据库原理及应用模拟试题4（Principleandapplicationofdatabasetest4）Test3Asinglechoice.(thetitleof10items,eachitemof2points,atotalof20points)1.inthedatabaseunderthemodeofinformationprocessing,occupiesacentralpositionis[]A.B.programsoftwareC.D.diskdata2..RandSaretwoyuan,andthenthetuplecalculusexpressio
2、ns
3、{tR(T)~(U)(S(U)u[1]=lambdat[2])}Therelationalalgebraexpressionisnotequivalent[]A.(PI1,2sigma2=3(R*S)B.1(2)PI,sigma2=1(R*S))C.PI1,2(R?S)D.3(4PI,sigma1=4(S*R))With3.rules:W(a,B,C,d)-R(a,B,x)aS(C,D,y)=x>yTherelationshipbetweentheexpressionandtherulesoftheheadisequivalentto[]A.PI1,2,4,5(
4、3>6(R?S)B.PI)1,2,4,5(sigma3>3(R*S))C.PI1,2,4,5(R?S)D.PI1,2,4,5(R?R)4.SQL,COUNT(lastname)fortheaggregationfunction[]ThenumberofA.calculationtuplesnumberB.tocalculatetheattributeC.D.tocalculatethenumberofnonnullvaluesinacolumnandanullvaluetocalculatethenumberofthenonnullvaluesinacolumn5.i
5、stherelationshipbetweenR(A,B,C)valuesareasfollows:ABC223234335Ofthefollowingstatementsistrue[]A.A,BB.establishedthefunctiondependencefunctionontherelationshipbetweenBCandAwasdependentontherelationshipbetweentheC.B,AD.establishedthefunctiondependencefunctionontherelationshipbetweenAandBC
6、wasdependentontherelationshipbetweenthe6.R(A,Bmodel,C,D,F)isformedonRFDinF={,AB,C,D,B},thenp={ACD,BD}relativetoF[]A.isalosslessdecomposition,butalsomaintainthedecompositionofFDB.isalosslessdecomposition,butdoesnotkeepthedecompositionofFDC.isnotalosslessdecomposition,butkeeptheFDdecompos
7、itionD.isnotalosslessdecomposition,donotkeepthedecompositionofFD7.inthe"weakentity"narrative,isnottrue[]A.weakentityexistsinthepremiseoftheparententityB.weakentityisdependentontheparententityTheC.oftheparententityandweakentityrelationcanbe1:1,1:NorM:NTheD.oftheparententityandweakentityc
8、ontactonly1:1or1:N8.iftherearenserialtransactionscheduling,soeffectiveschedulingaredifferent[]A.n2B.2nC.4nD.n!9.inthetraditionalSQLtechnology,theSELECTstatementusesthe"ORDERBY"clauseofthequeryresults,infact[]A.B.C.D.setpackagelistarrayInDDBS10.,usersorapplicationsshouldundersta
