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数据库系统运行的基本工作单位是事务。事务通常以BEGIN TRANSACTION语句开始，以COMMIT或ROLLBACK吾句结束。COMMIT表示 (22) ，ROLLBACK表示 (23) ...
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中级数据库系统工程师《单项选择》真题及答案
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下列关于事务的描述错误的是
事务运行过程中可以选择部分事务提交
事务是一个逻辑工作单元，是一个不可分割的工作单位
事务必须完整地执行，或者全都不执行（使数据库保持不变）
事务处理是保证数据库一致性状态的重要方法
数据库系统运行的基本工作单位是事务事务通常以BEGINTRANSACTION语句开始以COMM
回退到上一操作
回退到上一事务
事务执行失败，并做相应的回退动作
事务执行成功，并做相应的回退动作
数据库系统运行的基本工作单位是事务事务通常以BEGINTRANSACTION语句开始以COMMIT或
Loek_S(Q)
LoclX(Q)
Read(Q)
Write(Q)
数据库系统运行的基本工作单位是事务事务通常以BEGINTRANASCTION语句开始以COMM
物理数据库尚未更新，事务执行失败
物理数据库尚未更新，事务执行成功
物理数据库已更新，事务执行失败
物理数据库已更新，事务执行成功
数据库系统运行的基本工作单位是事务事务通常以BEGINTRANSACTION语句开始以COMMIT或
子程序
对象
原子
操作
数据库系统运行的基本工作单位是事务事务通常以BEGINTRANSACTION语句开始以COMM
子程序
对象
原子
操作
数据库系统运行的基本工作单位是事务事务通常以BEGINTRANSACTION语句开始以COMMIT或
物理数据库尚未更新，事务执行失败
物理数据库尚未更新，事务执行成功
物理数据库已更新，事务执行失败
物理数据库已更新，事务执行成功
数据库系统运行的基本工作单位是事务事务通常以BEGINTRANSACTION语句开始以COMM
Lock_S(Q)
Lock_X(Q)
Read(Q)
Write(Q)
数据库系统运行的基本工作单位是事务事务通常以BEGINTRANSACTION语句开始以COMM
可读未提交数据
读提交数据
可重复读
可串行化
数据库系统运行的基本工作单位是事务事务通常以BEGINTRANSACTION语句开始以COMMIT或
可读未提交数据
读提交数据
可重复读
可串行化
数据库应用系统中的基本逻辑工作单位是
一个查询
一个过程
一个事务
一个程序
数据库管理系统运行的基本工作单位是事务事务是用户定义的一个数据库操作序列这些操作序列要么全做要么全不
恢复性
内存驻留性
连续性
永久性
事务是数据库进行的基本工作单位如果一个事务执行失败且已经做过更新被重新恢复原状好像整个事务从来没有过
数据库系统运行的基本工作单位是事务事务通常以BEGINTRANSACTION语句开始以COMMIT或
回退到上一操作
回退到上一事务
事务执行失败，并做相应的回退动作
事务执行成功，并做相应的回退动作
数据库系统的逻辑工作单位是
SQL语句
事务
表
锁
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In85softwareonequestionofnear-universalinterestishowrapidlyWindowsNTwhichbeganshippinglastsummerwillbe86inthemarketplaceandforwhatuses.Forthemostpartobserversare87abouttheoperatingsystem’slongtermprospectsbutexpectittoremainon88ratherthandesktopsduring1994sayingthatitwon’tbecomeamainstreamproductuntil89PCstypicallyhave16to24MBofRAMwhichisunlikelytohappennextyear.
100whethertogowithasharedorswitchedfastLANtechnologyonceyoustarttomaxoutyoursharedEthernetoftoken-ringLANistoughcall.Usersandanalystsinvolvedin101high-speedLANshavelearnedthebenefitsofeach.Howevertherearetrade-offstoeachand102whichfastLANtechnologytochooseiscriticalfor103networkperformanceproblemsand104costlypurchasingmistakes.
Manywordprocessingprogramsincludespellchecker.Itchecksthespellingofeverywordina120bylookingupeachwordinitsdictionary.Iftheworddoesnotappearinthedictionarytheuseris121topossiblemisspellingandpossiblecorrectionsareoften122.Spellcheckerdoesnotrecognizeunusualpeoplenamesorspecializedtermsbutitwilloftenallowyoutocreateyourownpersonaldictionaryofspecializedwordsyouoftenuse.Spellcheckerisavaluableaidtoproofreadingbutitcannotcatchthe123ofonecorrectlyspelledwordforanothersuchasformforfrom.Thusitdoesnot124adocumentisfreeofspellingerrors.
Thegrowthofswitchinghas135anewgenerationofnetworkmanagementtoolsthathelp136copewiththechallenges137themtocorrelatedevicealarmsinorderto138pinpointrootcausesortomonitorservicelevelswithoutdependingonIPsubnetschemes.Thesenewtoolshavebecomeessentialtocopingwiththeprimary139effectofanytreatmentthatsignificantlyincreasesnetworkflexibility:addedcomplexity.
Alloftheseapplicationswillenhancethe130oflifeandspureconomicgrowth.OverhalfoftheU.S.workforceisnowinjobsthatareinformation131.ThetelecommunicationandinformationsectoroftheU.S.economynow132for12percentoftheGrossDomesticProductgrowingmuchfasterthananyothersectoroftheeconomy.Lastyearthe133inthissectorexceeded700billiondollars.TheU.S.exportedover48billiondollarsoftelecommunicationequipment134.
Manywordprocessingprogramsincludespellchecker.Itchecksthespellingofeverywordina120bylookingupeachwordinitsdictionary.Iftheworddoesnotappearinthedictionarytheuseris121topossiblemisspellingandpossiblecorrectionsareoften122.Spellcheckerdoesnotrecognizeunusualpeoplenamesorspecializedtermsbutitwilloftenallowyoutocreateyourownpersonaldictionaryofspecializedwordsyouoftenuse.Spellcheckerisavaluableaidtoproofreadingbutitcannotcatchthe123ofonecorrectlyspelledwordforanothersuchasformforfrom.Thusitdoesnot124adocumentisfreeofspellingerrors.
Therelationaldatabasemodelrequiresthedatabe110throughprogramsthatdon’trelyonthepositionofthedatainthedatabase.Thisisindirect111totheotherdatabasemodewheretheprogramhastofollowaseriesofpointerstothedataitseeks.Aprogram112arelationaldatabasesimplyasksforthedataitseeks;theDBMSperformsthenecessarysearchesand113theinformation.The114onhowthesearchisdonearespecifictotheDBMSandvaryfromproducttoproduct.
Forusersmicrokerneltechnologypromises90compactandsophisticatedoperatingsystemsthataretypically91acrossarangeofhardwareplatforms.Theseoperatingsystemswillbecustomizabletoletusersrunmultipleoperatingsystemandapplicationpersonalitiesontopofasinglemicrokernel92.Microkernelbasedsystemscanprovidethisflexibilitybecausethecoreoperatingsystemfunctionsare93fromthelargenumberofutilitiesfeaturesandextensionsthatarelayeredontopofthem.Asaresultupdatingandmaintainingoperatingsystemiseasiersincedevelopersdon’thavetomodifythe94everytimetheymustacidanewfeature.
Manywordprocessingprogramsincludespellchecker.Itchecksthespellingofeverywordina120bylookingupeachwordinitsdictionary.Iftheworddoesnotappearinthedictionarytheuseris121topossiblemisspellingandpossiblecorrectionsareoften122.Spellcheckerdoesnotrecognizeunusualpeoplenamesorspecializedtermsbutitwilloftenallowyoutocreateyourownpersonaldictionaryofspecializedwordsyouoftenuse.Spellcheckerisavaluableaidtoproofreadingbutitcannotcatchthe123ofonecorrectlyspelledwordforanothersuchasformforfrom.Thusitdoesnot124adocumentisfreeofspellingerrors.
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Alloftheseapplicationswillenhancethe130oflifeandspureconomicgrowth.OverhalfoftheU.S.workforceisnowinjobsthatareinformation131.ThetelecommunicationandinformationsectoroftheU.S.economynow132for12percentoftheGrossDomesticProductgrowingmuchfasterthananyothersectoroftheeconomy.Lastyearthe133inthissectorexceeded700billiondollars.TheU.S.exportedover48billiondollarsoftelecommunicationequipment134.
Networkmanagershavelong140practicalvoice-over-IPVOIPsolutions.VOIP141easenetworkmanagementanddecreasescostsbyconvergingacompany’stelephonyanddatainfrastructuresintoonenetwork.AndaVOIPsolutionimplementedatacompany’shead-quarterswithfar-reachingbranchofficescan142tremendousamountsof143inlongdistancephonebillsprovidedthatsolutiondeliversPOTS-likevoice144overtheInternet.
In85softwareonequestionofnear-universalinterestishowrapidlyWindowsNTwhichbeganshippinglastsummerwillbe86inthemarketplaceandforwhatuses.Forthemostpartobserversare87abouttheoperatingsystem’slongtermprospectsbutexpectittoremainon88ratherthandesktopsduring1994sayingthatitwon’tbecomeamainstreamproductuntil89PCstypicallyhave16to24MBofRAMwhichisunlikelytohappennextyear.
Therelationaldatabasemodelrequiresthedatabe110throughprogramsthatdon’trelyonthepositionofthedatainthedatabase.Thisisindirect111totheotherdatabasemodewheretheprogramhastofollowaseriesofpointerstothedataitseeks.Aprogram112arelationaldatabasesimplyasksforthedataitseeks;theDBMSperformsthenecessarysearchesand113theinformation.The114onhowthesearchisdonearespecifictotheDBMSandvaryfromproducttoproduct.
Alocal-areanetworkLANisacommunicationsnetworkthat125avarietyofdevicesandprovidesa126forinformationexchangeamongthosedevices.ThescopeoftheLANissmalltypicallyasinglebuildingoracluster丛ofbuildings.TheLANisusuallyownedbythesameorganizationthatownsthe127devices.TheinternaldatarateofLANisatleastseveralMb/s.ThebasicofLANcommunicationisbroadcasting.Ateachstationthereisatransmitter/receiverthatcommunicatesovera128sharedByotherstations.Atransmissionfromanyonestationis129toandreceivedbyallotherstations.
100whethertogowithasharedorswitchedfastLANtechnologyonceyoustarttomaxoutyoursharedEthernetoftoken-ringLANistoughcall.Usersandanalystsinvolvedin101high-speedLANshavelearnedthebenefitsofeach.Howevertherearetrade-offstoeachand102whichfastLANtechnologytochooseiscriticalfor103networkperformanceproblemsand104costlypurchasingmistakes.
Alocal-areanetworkLANisacommunicationsnetworkthat125avarietyofdevicesandprovidesa126forinformationexchangeamongthosedevices.ThescopeoftheLANissmalltypicallyasinglebuildingoracluster丛ofbuildings.TheLANisusuallyownedbythesameorganizationthatownsthe127devices.TheinternaldatarateofLANisatleastseveralMb/s.ThebasicofLANcommunicationisbroadcasting.Ateachstationthereisatransmitter/receiverthatcommunicatesovera128sharedByotherstations.Atransmissionfromanyonestationis129toandreceivedbyallotherstations.
Whenmostpeoplerefertomultimediatheygenerallymeanthecombinationoftwoormorecontinuousmediausuallywithsomeuser115.Inpracticethetwomediaarenormallyaudioandvideothisis116plusmoving117.Itshouldbe’obviousbynowthattransmittingmultimediamaterialinuncompressedformiscompletelyoutof118.Theonlyhopeisthatmassivecompressionispossible.Fortunatelyalargebodyofresearchoverthepastfewdecadeshasledtomanycompressiontechniquesandalgorithmsthatmakemultimediatransmission119.
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