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1、外文原文IntroductiontoSQLServerBySamuelRelationaldatabaseshavebeenaroundf30yearsbuttheywerenottheiginalkindofdatabasenaretheythenewestkindofdatabase.XMLobjectienteddatastructureshaveevolvedinrecentyears.Butrelationaldatabase

2、sarestillbyfarthemostpopularkindofdatabaseavailablewillbefsometimetocome.SQListheabbreviationofStructuredQueryLanguageitisfrelationaldatabasesasthetitleindicatesthisisonlyffresherwhohasjuststartedthecarrierwhoiswaitingto

3、openupthecarrierintheapplicationprogrammingside.ButthatdoesnotmeanthisarticleisatutialfafresherwhodoesnotknowanythingaboutSQL.ThisarticleismeantfwhoalreadyhavealittleknowledgeinSQLwanttoimproveit.WhatDoesSQLDoFirstSQList

4、hepremiertoolfviewinginfmationfromarelationaldatabase.Itdoesn’tjustgiveyouadatadump.SQLgivesyousophisticatedtoolstosummarizeconsolidatecalculatefromthedata.Usingtablerelationshipsdatacanbecombinedfrommultipletablesinanum

5、berofways.WithaproperlydesigneddatabaseSQLcananswerpracticallyanyquestionaboutthedata.SecondSQLprovidescommstomanipulatethedatainarelationaldatabase.Recdscanbeupdatedaddedtodfromatable.HereisSQLasadatabaselanguagereallys

6、hines.ProceduralprogramminglanguagessuchasBASICmightrequireseverallinesofcodetoupdatearecdinadatabasetable.Inadditionproceduralprogramminglanguageswouldhavetousesomestofloopingstructuretorepeatthisprocessoneveryrecd.SQLo

7、peratesonanentiresetofrecdsallatthesametime.SQLislikehaikufprogrammersoftenadozenwdsfewercanchangethoussofrecds.FinallySQLisacompletedatadefinitionlanguage(DDL).Thedatabaseitselfcanbecreatedalongwithalltablesfieldsprimar

8、ykeysrelationships.Addtothattherecdcommsyoucanhaveacompletedatabaseallitsdataexpressedinprogrammingcode.Thisgreatlyenhancesadatabaseprogrammer’sabilitytowkremotelytoptdataenhancementsamongvariousinstallations.Theprerequi

9、siteflearningSQLisknowledgeinDiscreteMathematics(SetTheyRelationsFunctions).AlthoughitisnotnecessarytolearnallthetheemsprooffthetheemsintheDiscreteMathematicsyoushouldhavelearnedthebasicprimaryonit.(SodefiningUNIQUENOTNU

10、LLconstraintisnotequivalenttoprimarykey).SQLserverwillcreateaClusteredindexwhileyoucreateaprimarykey.Primarykeysshouldbecarefullydefinedsincebasedonitotherrelationsaredefined.Polydesignedprimarykeyswillaffectupdateoperat

11、ions.Primarykeysaredifferentfromwhichareusedfpaperwk.FeignKeyTheprimarykeyofoneofthetablesisalmostalwaysinvolvedintherelationship.Thefieldintheothertableontheotherendofthatrelationshipiscalledthefeignkey.Thetermsimplyref

12、erstothefactthatthisfieldiskeytorelatingtoafeign(other)table.IntheLyricMusicdatabasethereisarelationshipbetweenartiststitles.TheArtistIDfieldistheprimarykeyintheArtiststable.TherefetheArtistIDfieldintheTitlestableisafeig

13、nkey.ItrelatestheTitlestabletotheprimarykeyintheArtiststable.Mosttablerelationshipscanbedescribedasonetomany.Inaonetomanyrelationshipasinglerecdinthefirsttablecanberelatedtomanyrecdsinthesecondtable.Howevereachrecdinthes

14、econdtablerelatestoonlyonerecdinthefirsttable.Inadditiontoonetomanyrelationshiptablescanhaveonetoonerelationships.Butthesearemuchlesscommon.Server–ClientInClientServertechnologyaserverisaprogramwhichdoesallthejobsthatisr

15、equestedbytheclientClientisaprogramwhichdependsontheServertoaccomplishitstask.ClientismainlyusedtointeractwithUsersmostServersoftwaredoesn’thavedirectinteractionwithUsers.ADBMSshouldhavethefollowingfunctionality–Interact

16、ionwithusers(developers)ManagingData.SincethesetwofunctionalitiesareentirelydifferentmodernDBMSisdividedintotwomeparts.AlmostallcurrentDBMShasthefollowingmodule–Serveronemeclients.Aservermoduleisprogramwhichmanagesthedat

17、ahlesrequestsfromtheclientapplications.ItinterpretstheSQLqueriesreturnsresultsbacktotheclients.AclientprogramisaprogramwhichsendsSQLcommstoservergetstheresult.Clientprogramdoesnotknowthedetailedundergroundstructureofthes

18、erver.SQLServer2000runsasaserviceinNTbasedmachines.YouhavetoestablishaconnectiontotheserverfirstifyouwanttodosomeSQLoperation.SQLServerusesLocalwkIPC(Interprocesscommunication)tocommunicatewiththeclients.SeeBooksOnlinefm

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