db2学习总结文档

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1、`1.Adatabasemanagementsystemprovidesasetofintegrateddatamanagementservicesortoolswhichareusedtomaintainandmanagelogicalgroupingsofdataorinformation.Inthisbranchofmathematics,atableiscalledarelation.2.Codd'soriginaltheorywasbasedon12principles.(1)Thefirstist

2、hatalldatainanRDBMSisstoredintables.(2)Anotherprincipleisthatyouneedalanguagetoretrieveormanipulatedatainthesetables.ThislanguageisknownasSQLandispartoftherelationaltheory.3.Atableconsistsofcolumnsandrows.Columnsaretheattributesoftheentity.Theyarethesamefor

3、everyparticularinstanceoftheentity.Everyparticularinstanceoftheentityisarow.Rowsarenotusuallystoredinanyparticularorder.Thereisonlyonevalueateveryrowandcolumnpositioninatable.Thismeansthatalldatavaluesareatomic.4.Theremustbesomewaytoidentifyuniquelyjustonei

4、nstanceorrowofatableinordertomanipulatethedatainit.Theuniquekeywillallowyoutodojustthat.5.TherearetwotermsyoumayheartodescribeSQL.Thefirstisnon-navigational.ThismeansthatyouonlyneedtotellDB2,throughSQL,whatdatayouwant.YoudonotneedtospecifyhowDB2istogetthatd

5、ata.Byusingtheoptimizer,DB2determinesthebestaccesspath.Forexample,itdecideswhethertouseanindextoretrievedata.SQLisalsoanon-procedurallanguage.AprocedurallanguageisaprogramminglanguagesuchasCorCOBOL.SQLisnotaprogramminglanguage.Itdoesnotdoloopingorgothroughe

6、xtensiveif-then-elsestepsonerecordatatime.SQLhandlesasetofrecordsinatableandcanbeembeddedintoaprogramminglanguagetotakeadvantageofthecapacityofthelanguagetocarryoutprocedurallogiconthatdata.6.DataManipulationLanguage(DML)allowsyoutoretrieveandmanipulatedata

7、.SELECTisyourbasicreadstatement.BothSELECTandUPDATEworkatthecolumnlevel.INSERTandDELETEfunctionattherowlevel.DataDefinitionLanguage(DDL)allowsyoutoCREATEandmaintainthephysicaldatastructuresorobjectsinyourdatabase.YouCREATEatableorindex.TheALTERstatementallo

8、wsyoutoaddacolumntotheendofatable.Ifyounolongerneedanobject,youcansimplyDROPthatobject.ControlLanguageprovidesthecontrolstatementsthatgoverndatasecurity.YoumustbeauthorizedtousevariousobjectsinDB2.Youn