Schema changes - IBM

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In order to maintain the integrity of the relationship between the system-period temporal table and its associated history table, only certain changes to ... Schemachanges Inordertomaintaintheintegrityoftherelationship betweenthesystem-periodtemporaltableanditsassociatedhistory table,onlycertainchangestotheschemaofasystem-periodtemporal tablearepermitted.Anychangesthatwouldresultinthelossof dataarerestricted. Youcanmakethefollowingchangestoyoursystem-periodtemporal tables.Thesechangesareimplicitlypropagatedtotheassociated historytableifyouhavetheappropriateprivileges.Thesechanges cannotbeexplicitlymadetothehistorytable. ADDCOLUMN(exceptgeneratedcolumns) RENAMECOLUMN ALTERCOLUMN(incaseswherenohistorydataislost).Forexample, alteringthedatatypeofacolumnfromVARCHAR(50)toVARCHAR(100), orfromINTEGERtoDECIMALispermitted.However,thereversechange fromVARCHAR(100)toVARCHAR(50),orfromDECIMALtoINTEGERisblocked becauseitwouldreducethelengthorprecisionofacolumnandlikely causealossofdata. Youcannotmakethefollowingchangestoyoursystem-periodtemporal tablesbecausedatawouldlikelybelost: DROPCOLUMN ADDCOLUMN(generated) ALTERCOLUMN(incaseswherehistorydatamightbelost).For example,alteringthedatatypeofacolumnfromVARCHAR(50)toVARCHAR(100), orfromINTEGERtoDECIMALispermitted.However,thereversechange fromVARCHAR(100)toVARCHAR(50),orfromDECIMALtoINTEGERisblocked becauseitwouldreducethelengthorprecisionofacolumn. Versioningestablishesalinkbetweenyoursystem-periodtemporal tableanditsassociatedhistorytable.Whenversioningisactive, certainALTERTABLEoperationsareblockedonsystem-periodtemporal tablesandhistorytables. ALTERTABLEDROPPERIOD ALTERTABLEADDMATERIALIZED ALTERTABLEACTIVATENOTLOGGEDINITIALLY ALTERTABLEADDSECURITYPOLICY ALTERTABLEDROPSECURITYPOLICY ALTERTABLESECUREDWITHALTER ALTER TABLEoperationsthatarenotshowninthepreviouslistaresupported, butarenotpropagatedfromasystem-periodtemporaltabletoits historytable. Additionally,RENAMEINDEXandRENAMETABLEaresupported,but arenotpropagatedfromasystem-periodtemporaltabletoitshistory table. Parenttopic:System-periodtemporaltables

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