db2学习总结文档.docx

《db2学习总结文档.docx》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。

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

2、sstoredintables.(2)Anotherprincipleisthatyouneedalanguagetoretrieveormanipulatedatainthesetables.ThislanguageisknownasSQLandispartoftherelationaltheory.3.Atableconsistsofcolumnsandrows.Columnsaretheattributesoftheentity.Theyarethesameforeveryparticularinstanceoftheentity.Every

3、particularinstanceoftheentityisarow.Rowsarenotusuallystoredinanyparticularorder.Thereisonlyonevalueateveryrowandcolumnpositioninatable.Thismeansthatalldatavaluesareatomic.4.Theremustbesomewaytoidentifyuniquelyjustoneinstanceorrowofatableinordertomanipulatethedatainit.Theunique

4、keywillallowyoutodojustthat.5.TherearetwotermsyoumayheartodescribeSQL.Thefirstisnon-navigational.ThismeansthatyouonlyneedtotellDB2,throughSQL,whatdatayouwant.YoudonotneedtospecifyhowDB2istogetthatdata.Byusingtheoptimizer,DB2determinesthebestaccesspath.Forexample,itdecideswheth

5、ertouseanindextoretrievedata.SQLisalsoanon-procedurallanguage.AprocedurallanguageisaprogramminglanguagesuchasCorCOBOL.SQLisnotaprogramminglanguage.Itdoesnotdoloopingorgothroughextensiveif-then-elsestepsonerecordatatime.SQLhandlesasetofrecordsinatableandcanbeembeddedintoaprogra

6、mminglanguagetotakeadvantageofthecapacityofthelanguagetocarryoutprocedurallogiconthatdata.6.DataManipulationLanguage(DML)allowsyoutoretrieveandmanipulatedata.SELECTisyourbasicreadstatement.BothSELECTandUPDATEworkatthecolumnlevel.INSERTandDELETEfunctionattherowlevel.DataDefinit

7、ionLanguage(DDL)allowsyoutoCREATEandmaintainthephysicaldatastructuresorobjectsinyourdatabase.YouCREATEatableorindex.TheALTERstatementallowsyoutoaddacolumntotheendofatable.Ifyounolongerneedanobject,youcansimplyDROPthatobject.ControlLanguageprovidesthecontrolstatementsthatgovern

8、datasecurity.YoumustbeauthorizedtousevariousobjectsinDB2.Youn