外文翻译4

大连交通大学2012届本科生毕业设计（论文）外文翻译1ManagementCenterofMySQLAuthors:Lauderdale,JohnTsang,DannyH.K.Baciu,GeorgeIssueDate:2006Citation:ProceedingsofIEEEVisual'96,Melbourne,Australia,February2006,p.447-458Database(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”,andmultiplerelationscanbemathematicallyassociatedtoyield大连交通大学2012届本科生毕业设计（论文）外文翻译2desiredinformation.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.DBMSStructuringTechniquesSequential,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,wouldbelinkedtonextinvoicesforthe大连交通大学2012届本科生毕业设计（论文）外文翻译3customer.Thelastinvoiceinthechainwouldbeidentifiedbytheuseofaspecialcharacterasapointer.Hierarchical(tree)structures.Inthislogicalapproach,dataunitsarestructuredinmultiplelevelsthatgraphica