毕业论文外文翻译MySQL数据库管理中心.docx

毕业论文外文翻译MySQL数据库管理中心.docx

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毕业论文外文翻译MySQL数据库管理中心

ManagementCenterofMySQL

Authors:

Lauderdale,John

Tsang,DannyH.K.

Baciu,George

IssueDate:

2006

Citation:

ProceedingsofIEEEVisual'96,Melbourne,Australia,February2006,p.447-458

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.Recordsinacustomerm