asadv63题解析和机经63题答案解析

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1、1.Whenattemptingtominimizememoryusage^themostefficientwaytodogroupprocessingwhenusingtheMEANSprocedureistouse:A.theBYstatement.B.GROUPBYwiththeNOTSORTEDspecification.C.theCLASSstatement.D.multipleWHEREstatements.ShapeoftheDataMostEfficientToolsarelativelysmallnumberofdistinctcombinatio

2、nsofvaluesoftheclassvariable—thesummarizeddatacontains10%orfeweroftheobservationsintheoriginaldataset•PROCMEANS(orPROCSUMMARY)•PROCREPORT•PROCTABULATEarelativelylargenumberofdistinctcombinationsofvaluesoftheclassvariable—thesummarizeddatacontainsmorethan10%oftheobservationsintheorigina

3、ldataset•PROCSQL•DATAstepandPROCSORT曲UsingaGROUPBYstatementinPROCSQLissimilarinCPUusagetoaPROCSORTstepfollowedbyaDATAstep.ComparingResourceUsageacrossThreeTechniquesforUsingPROCMEANSThethreetechniquesforsummarizingdataforspecificcombinationsofclassvariables(allbutthebasicPROCMEANSstep)

4、differinresourceusageasfollows:•TheTYPESstatementinaPROCMEANSstepusesthefewestresources・•AprogramthatcontainstheNWAYoptioninmultiplePROCMEANSstepsusesthemostresourcesbecauseSASmustreadthedatasetseparatelyforeachPROCMEANSstep.•TheWHERE二datasetoptioninaPROCMEANSstepusesmoreresourcesthant

5、heTYPESstatementinPROCMEANSbecauseSASmustcalculateallpossiblecombinationsofclassvariablesbeforesubsetting.However,theWHERE=datasetoptioninPROCMEANSusesfewerresourcesthantheNWAYoptioninmultiplePROCMEANSsteps.2.TheSASdatasetWORK.CHECKhasavariablenamedId_Codeinit.WhichSQLstatementwouldcre

6、ateanindexonthisvariable?A.createindexTdCodeonWORK.CHECK;B.createindex(TdCode)onWORK.CHECK;A.makeindex二Id_CodefromWORK.CHECK;B.defineindex(Id_Code)inWORK.CHECK;关于在SQL语句中创建INDEX的语句格式如下：Generalform,CREATEINDEXstatement:CREATEINDEXindex-nameONtable-name(column-name-l<,•••column-na

7、me-n»;示例语句：/*creatingasimpleindex*/datacrackman;inputid_codename$@;datalines;1java2c++3dephi4asp5c#.netprocsql;createindexid_codeonwork•crackman;quit;log提示简单索引idcode已经建立或者使用：procsql;createindexid_codeonwork•crackman(id_code);quit;之所以括号内的column-name是可选项，是应为在建立Simpleindex时，index-name必须