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1、外文原文IntroductiontoSQLServerBySamuelRelationaldatabaseshavebeenaroundfor30years,buttheywerenottheoriginalkindofdatabase,noraretheythenewestkindofdatabase.XMLandobject-orienteddatastructureshaveevolvedinrecentyears.Butrelationaldatabasesarestillbyfarthemostpopularkindofdatabaseav
2、ailableandwillbeforsometimetocome.SQListheabbreviationofStructuredQueryLanguageanditisforrelationaldatabases,asthetitleindicatesthisisonlyforfresherwhohasjuststartedthecarrierorwhoiswaitingtoopenupthecarrierintheapplicationprogrammingside.Butthatdoesnotmeanthisarticleisatutoria
3、lforafresherwhodoesnotknowanythingaboutSQL.ThisarticleismeantforwhoalreadyhavealittleknowledgeinSQLandwanttoimproveit.WhatDoesSQLDo?First,SQListhepremiertoolforviewinginformationfromarelationaldatabase.Itdoesn’tjustgiveyouadatadump.SQLgivesyousophisticatedtoolstosummarize,conso
4、lidate,andcalculatefromthedata.Usingtablerelationships,datacanbecombinedfrommultipletablesinanumberofways.Withaproperlydesigneddatabase,SQLcananswerpracticallyanyquestionaboutthedata.Second,SQLprovidescommandstomanipulatethedatainarelationaldatabase.Recordscanbeupdatedandaddedt
5、oordeletedfromatable.HereisSQLasadatabaselanguagereallyshines.Proceduralprogramminglanguages,suchasBASIC,mightrequireseverallinesofcodetoupdatearecordinadatabasetable.Inaddition,proceduralprogramminglanguageswouldhavetousesomesortofloopingstructuretorepeatthisprocessoneveryreco
6、rd.SQLoperatesonanentiresetofrecordsallatthesametime.SQLislikehaikuforprogrammers;oftenadozenwordsorfewercandeleteorchangethousandsofrecords.Finally,SQLisacompletedatadefinitionlanguage(DDL).Thedatabaseitselfcanbecreatedalongwithalltables,fields,primarykeys,andrelationships.Add
7、tothattherecordinsertcommands,andyoucanhaveacompletedatabaseandallitsdataexpressedinprogrammingcode.Thisgreatlyenhancesadatabaseprogrammer’sabilitytoworkremotelyortoportdataenhancementsamongvariousinstallations.TheprerequisiteforlearningSQLisknowledgeinDiscreteMathematics(SetTh
8、eory,RelationsandFunctions).Althoughitisnotnecessaryto
