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1、数据库原理及应用模拟试题4（Databaseprincipleandapplicationsimulationtestquestions4）Mockquestions3Asinglechoice.(thetitleof10items,eachitemof2points,atotalof20points)1.indatabaseprocessing,thecentrallocationis[...]A.data,B.program,C.software,D.disk2.setRandSaretwoyuanr
2、elationship,thenwithtuplecalculusexpression
3、{tR(T)~(U)(S(U)u[1]=lambdat[2])}Anequivalentrelationalgebraexpressionis[...]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>yTheexpression
4、equivalenttotheheadoftheaboveruleis[...]A.PI1,2,4,5(sigma3>6(R,S)),B.,PI1,2,4,5(sigma3>3(R*S))C.PI1,2,4,5(R,S),D.,PI1,2,4,5(R,R)In4.SQL,theaggregatefunctionCOUNT(columnname)isused[[]]A.calculatesthenumberoftuplesandB.calculatesthenumberofattributesC.count
5、sthenumberofnonnullvaluesinacolumn.D.calculatesthenumberofnonnullandnullvaluesinacolumn5.withrelationalR(A,B,C)valuesareasfollows:ABC223234335Thefollowingstatementiscorrect[[]]TheA.functionreliesonA=BtosetuptheB.functionintheaboverelation.ThedependencyBC=
6、AissetupintheaboverelationTheC.functionreliesonB=AtosetuptheD.functionintheaboverelation.ThedependencyA=BCissetupintheaboverelation6.R(A,Bmodel,C,D,F)isformedonRFDinF={,AB,C,D,B},thenp={ACD,BD}relativetoF[]A.islosslessjoindecomposition,anditalsomaintainst
7、hedecompositionofFDB.islosslessjoindecomposition,butdoesnotmaintainthedecompositionofFDC.isnotlosslessjoindecomposition,butmaintainsthedecompositionofFDD.isneitherlosslessjoindecompositionnorFDdecomposition7.,inthenarrativeoftheweakentity,itisincorrecttha
8、t[...]TheexistenceofA.weakentitiesisbasedontheexistenceoftheparententityTheB.weakentitydependsontheexistenceoftheparententityTheC.parententityisassociatedwithaweakentitythatcanbe1:1,1:N,orM:NTheD.parententityisassociatedwithaweakentityonly1:1or1:N8.,ifthe
9、rearentransactionserialscheduling,thendifferenteffectivescheduling[[]]A.n2B.2nC.4nD.n!9.intraditionalSQLtechniques,theresultsoftheSELECTstatementqueryusingthe"ORDERBY"clauseareactually[[]]A.array,B.list,C.package,D.
