电子数据库外文翻译文献.docx
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电子数据库外文翻译文献.docx
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电子数据库外文翻译文献
电子数据库外文翻译文献
(文档含中英文对照即英文原文和中文翻译)
原文:
ManagementCenterofMySQL
Database(sometimesspelleddatabase)isalsocalledanelectronicdatabase,referringtoanycollectionsofdata,orinformation,thatisspeciallyorganizedforrapidsearchandretrievalbyacomputer.Databasesarestructuredtofacilitatethestorage,retrieval,modificationanddeletionofdatainconjunctionwithvariousdata-processingoperations.Databasecanbestoredonmagneticdiskortape,opticaldisk,orsomeothersecondarystoragedevice.
Adatabaseconsistsofafileorasetoffiles.Theinformationinthethesefilesmaybebrokendownintorecords,eachofwhichconsistsofoneormorefieldsarethebasicunitsofdatastorage,andeachfieldtypicallycontainsinformationpertainingtooneaspectorattributeoftheentitydescribedbythedatabase.Usingkeywordsandvarioussortingcommands,userscanrapidlysearch,rearrange,group,andselectthefieldsinmanyrecordstoretrieveorcreatereportsonparticularaggregatesofdata.
Databaserecordsandfilesmustbeorganizedtoallowretrievaloftheinformation.Earlysystemwerearrangedsequentially(i.e.,alphabetically,numerically,orchronologically);thedevelopmentofdirect-accessstoragedevicesmadepossiblerandomaccesstodataviaindexes.Queriesarethemainwayusersretrievedatabaseinformation.Typicallytheuserprovidesastringofcharacters,andthecomputersearchesthedatabaseforacorrespondingsequenceandprovidesthesourcematerialsinwhichthosecharactersappear.Ausercanrequest,forexample,allrecordsinwhichthecontentofthefieldforaperson’slastnameisthewordSmith.
Inflatdatabases,recordsareorganizedaccordingtoasimplelistofentities;manysimpledatabasesforpersonalcomputersareflatinstructure.Therecordsinhierarchicaldatabasesareorganizedinatreelikestructure,witheachlevelofrecordsbranchingoffintoasetofsmallercategories.Unlikehierarchicaldatabases,whichprovidesinglelinksbetweensetsofrecordsatdifferentlevels,networkdatabasescreatemultiplelinkagesbetweensetsbyplacinglinks,orpointers,toonesetofrecordsinanother;thespeedandversatilityofnetworkdatabaseshaveledtotheirwideuseinbusiness.Relationaldatabasesareusedwhereassociationsamongfilesorrecordscannotbeexpressedbylinks;asimpleflatlistbecomesonetable,or“relation”,andmultiplerelationscanbemathematicallyassociatedtoyielddesiredinformation.Object-orienteddatabasesstoreandmanipulatemorecomplexdatastructures,called“objects”,whichareorganizedintohierarchicalclassesthatmayinheritpropertiesfromclasseshigherinthechain;thisdatabasestructureisthemostflexibleandadaptable.
Theinformationinmanydatabasesconsistsofnatural-languagetextsofdocuments;Smalldatabasescanbeusedbyindividualsathome.Theseandlargerdatabaseshavebecomeincreasinglyimportantinbusinesslife.Typicalcommercialapplicationsincludeairlinereservations,productionmanagement,medicalrecordsinhospitals,andlegalrecordsofinsurancecompanies.Thelargestdatabasesareusuallymaintainedbygovernmentalagencies,businessorganizations,anduniversities.Thesedatabasesmaycontaintextsofsuchmaterialsascatalogsofvariouskinds.Referencedatabasescontainbibliographiesorindexesthatserveasguidestothelocationofinformationinbooks,periodicals,andotherpublishedliterature.Thousandsofthesepubliclyaccessibledatabasesnowexist,coveringtopicsrangingfromlaw,medicine,andengineeringtonewsandcurrentevents,games,classifiedadvertisements,andinstructionalcourses.Professionalssuchasscientists,doctors,lawyers,financialanalysts,stockbrokers,andresearchersofalltypesincreasinglyrelyonthesedatabasesforquick,selectiveaccesstolargevolumesofinformation.
DBMSStructuringTechniques
Sequential,direct,andotherfileprocessingapproachesareusedtoorganizeandstructuredatainsinglefiles.ButaDBMSisabletointegratedataelementsfromseveralfilestoanswerspecificuserinquiriesforinformation.Thatis,theDBMSisabletostructureandtietogetherthelogicallyrelateddatafromseverallargefiles.
LogicalStructures.Identifyingtheselogicalrelationshipsisajobofthedataadministrator.Adatadefinitionlanguageisusedforthispurpose.TheDBMSmaythenemployoneofthefollowinglogicalstructuringtechniquesduringstorage,access,andretrievaloperations.
Liststructures.Inthislogicalapproach,recordsarelinkedtogetherbytheuseofpointers.Apointerisadataiteminonerecordthatidentifiesthestoragelocationofanotherlogicallyrelatedrecord.Recordsinacustomermasterfile,forexample,willcontainthenameandaddressofeachcustomer,andeachrecordinthisfileisidentifiedbyanaccountnumber.Duringanaccountingperiod,acustomermaybuyanumberofitemsondifferentdays.Thus,thecompanymaymaintainaninvoicefiletoreflectthesetransactions.Aliststructurecouldbeusedinthissituationtoshowtheunpaidinvoicesatanygiventime.Eachrecordinthecustomerintheinvoicefileincludesafield,itpointedtothelocationofthefirstinvoicerecordininvoicefile,thisinvoicerecord,inturn,wouldbelinkedtonextinvoicesforthecustomer.Thelastinvoiceinthechainwouldbeidentifiedbytheuseofaspecialcharacterasapointer.
Hierarchical(tree)structures.Inthislogicalapproach,dataunitsarestructuredinmultiplelevelsthatgraphicallyresemblean“upsidedown”treewiththerootatthetopandthebranchesformedbelow.There’sasuperior-subordinaterelationshipinahierarchical(tree)structure.Belowthesingle-rootdatacomponentaresubordinateelementsornodes,inturn,eachelementorbranchinthisstructurebelowtheroothasonlyasingleowner.Thus,acustomerownsaninvoice,andtheinvoicehassubordinateitems.Thebranchesinatreestructurearenotconnected.
NetworkStructures.Unlikethetreeapproach,whichdoesnotpermittheconnectionofbranches,thenetworkstructurepermitstheconnectionofthenodesinamultidirectionalmanner.Thus,eachnodemayhaveseveralownersandmay,inturn,ownanynumberofotherdataunits.Datamanagementsoftwarepermitstheextractionoftheneededinformationfromsuchastructurebybeginningwithanyrecordinafile.
Relationalstructures.Arelationalstructureismadeupofmanytables.Thedataarestoredintheformof“relations”inthesetables.Thisisarelativelynewdatabasestructuringapproachthat’sexpectedtobewidelyimplementedinthefuture.
PhysicalStructures.Peoplevisualizeorstructuredatainlogicalwaysfortheirownpurposes.Thus,recordsR1andR2mayalwaysbelogicallylinkedandprocessedinsequenceinoneparticularapplication.However,inacomputersystemit’squitepossiblethattheserecordsthatarelogicallycontiguousinoneapplicationarenotphysicallystoredtogether.Rather,thephysicalstructureoftherecordsinmediaandhardwaremaydependnotonlyontheI/Oandstoragedevicesandstoragetechniquesused,butalsoonthedifferentlogicalrelationshipsthatusersmayassigntothedatafoundinR1andR2.Forexample,R1andR2mayberecordsofcreditcustomerswhohaveshipmentssendtothesameblockinthesamecityevery2weeks.Fromtheshippingdepartmentmanager’sperspective,then,R1andR2aresequentialentriesonageographicallyorganizedshippingreport.ButintheA/Rapplication,thecustomersrepresentedbyR1andR2maybeidentified,andtheiraccountsmaybeprocessed,accordingtotheiraccountnumberswhicharewidelyseparated.Inshort,then,thephysicallocationofthestoredrecordsinmanycomputer-basedinformationsystemsisinvisibletousers.
DatabaseManagementFeaturesofMySQL
MySQLincludesmanyfeaturesthatmakethedatabaseeasiertomanage.We’vedividedthediscussioninthissectionintothreecategories:
MySQLEnterpriseManager,add-onpacks,backupandrecovery.
1.MySQLEnterpriseManager
AspartofDatabaseServer,MySQLprovidestheMySQLEnterpriseManager(EM),adatabasemanagementtoolframeworkwithagraphicalinterfaceusedtomanagedatabaseusers,instances,andfeatures(suchasreplication)thatcanprovideadditionalinformationabouttheMySQLenvironment.
PriortotheMySQL8idatabase,theEMsoftwarehadtobeinstalledonWindows95/98orNT-basedsystemsandeachrepositorycouldbeaccessedbyonlyasingledatabasemanageratatime.NowyoucanuseEMfromabrowserorloaditontoWindows95/98/2000orNT-basedsystems.MultipledatabaseadministratorscanaccesstheEMrepositoryatthesametime.IntheEMrepositoryforMySQL9i,thesuperadministratorcandefineservicesthatshouldbedisplayedonotheradministrators’consoles,andmanagementregionscanbesetup.
2.Add-onpacks
Severaloptionaladd-onpacksareavailableforMySQL,asdescribedinthefollowingsections.Inadditiontothesedatabase-managementpacks,managementpacksareavailableforMySQLApplicationsandforSAPR/3.
(1)standardManagementPack
TheStandardManagementPackforMySQLprovidestoolsforthemanagementofsmallMySQLdatabases(e.g.,MySQLServer/StandardEdition).Featuresincludesupportforperformancemonitoringofdatabasecontention,I/O,load,memoryuseandinstance,sessionanalysis,indextuning,andchangeinvestigationandtracking.
(2)DiagnosticsPack
YoucanusetheDiagnosticPacktomonitor,diagnose,andmaintainthehealthofEnterpriseEditiondatabases,operatingsystems,andapplications.Withbothhistoricalandreal-timeanalysis,itcanautomaticallyavoidproblemsbeforetheyoccur.Thepackalsoprovidescapa
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