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1、oraclelob类型存储浅析（OracleLOB类型存储浅析）BriefanalysisofOracleLobtypestoragePersonalclassification:Orac1eFoundationInOracle,avarietyofdatatypesareprovidedfordatatablefieldscolumnandPL/SQLlanguage,inordertocopewithvarioustypesofactualdevelopment・TheLobtypeisOracle,whichintroducesadatatypethatholdslargeobje
2、cts.Whenweconsidertheuseofdatafiles(decimal,binary),images,andevenaudioinformationasadatabasecarrier,weneedtouselobtypedata・Atpresent,Orac1esupportedLobtypesineludefoursubtypes(subtype),CLOB,BLOB,NLOBandBFILErespectively.Amongthem,CLOB,BLOBandNLOBarealldatastoredinthedatabase,andthecoreoftheBFILE
3、typepreservationisthefilepointer,therealfileisstoredoutsidethedatabase・Comparedwithtraditionaldatatypes,lobtypedatahasmanyspecialfeaturesbothinmanagementandspaceusage.Thisarticleintroducessomebasicstoragefeaturesoflobtypes・1,environmentaipreparationanddatasegmentsegmentcharacteristicsWechosetodoe
4、xperimentsunderOracle10gR2.SQL>select*fromv$version;BANNEROrac1eDatabaselOgEnterpriseEditionRe1easel0・2.0・1・0一ProdPL/SQLReleaselO.2.0.1.0-ProductionCORE10.2.0.1.0ProductionTNSfor32-bitWindows:VersionlO.2.0.1.0-ProductionNLSRTLVersionlO.2.0.1.0-ProductionUsingthecreatetablecommand,anexperimentalda
5、tatableTcanbeconstructed・SQL>createtablet(IDnumber,ClCLOB);TablecreatedForageneraldatatable,adatatablewillonlycorrespondtoastoreddatasegmentdatasegmentobject・Thespecialcasehereisthepartitiontable,whichusuallycorrespondstoaseparatestorageobject・Whenthedatatablecontainsalobtypedatacolumn,therewillb
6、eauniqueparagraphobjecttobuild・SQL>selectsegmentname,segmenttype,tablespacenamefromusersegments;SEGMENT_NAMESEGMENT_TYTABLESPACE_NAMESYS_L0B0000056069C00002$$L0BSEGMENTUSERSTTABLEUSERSSYS_IL0000056069C00002$$L0BINDEXUSERS(length,reason,irrelevantobjectomitted・)9rowsselectedWefoundthat,inadditiont
7、otheconventionaldatasegmentT,thereweretwoadditionalsegmentobjectsclearlynamedforthesystem,andthetypeswerelobsegmentandlobindexrespectively.ForaOraclelobtypedatatable,adatatablewithlobcolumnsiscreatedtocorrespondtomulti
