[SAS课件]-斯坦福大学sas教学课件SAS-SQL.ppt

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1、HRP223–2005Topic9-WorkingwithMultipleTablesCopyright©1999-2005LelandStanfordJuniorUniversity.Allrightsreserved.Warning:Thispresentationisprotectedbycopyrightlawandinternationaltreaties.Unauthorizedreproductionofthispresentation,oranyportionofit,mayresultinseverecivilandcriminalpenaltiesandwi

2、llbeprosecutedtomaximumextentpossibleunderthelaw.CombiningData(1)Whenyouhavedatasetsthatneedtobecombinedyoucandosixdifferentthings:concatenatinginterleavingonetoonetablereadingonetoonetablematchingmatchedmergingUpdatingThesethingscanbedonewithdatastepsorwithprocsql.IuseandrecommendSQLbutIwil

3、lshowyoutheSASwaysoyoucanreadotherpeople’scode.CombiningData(2)Concatenating*typicalmethod;dataall_dx;setdxyr1dxyr2;run;*fastermethod;procappendbase=dxyr1data=dxyr2;run;commonvariablenamesdatasetnamesCombiningData(3)Interleavingdataall_dx;setdxyr1dxyr2;bydxyear;run;CombiningData(4)One-to-one

4、ReadorMergedatadatetype;setdxyr1;setcancer;run;datadatetype;mergedxyr1cancer;run;CombiningData(5)MatchMergedatanew;mergepers_datcan_dat;byid;run;CombiningData(6)Updatingdatanew;updatebirth_dxtheup;byid;run;DatabaseRealitySincethe1980’s,thedominantmodelfordatabaseshasbeen“relational.”Relation

5、aldatabasesusemultipletablestostoredata.Eachofthesetables,whichlookjustlikespreadsheetpages,storesrelatedinformation.Theprimarygoalsinlayingoutarelationaldatabasearetoremoveredundancyandextravariables.Thisprocessiscallednormalization.NormalizationInanormalizeddatabasethereisalwaysavariable(o

6、rsetofvariables)thatcanbeusedtolinkthetables,butotherthanthat,thesameinformationisnotrepeatedinatableoracrosstables.Thisbuysyoulotsofspaceandspeed!ANormalizedDatabaseIntheHas_CAlibrary:IDisakeyjoiningthemasterandcancertables.IDanddxDatemakeajointkey.IDisakeyjoiningthemasteranddudetables.hNam

7、eisakeyrelatingthetreatmentandhospitaltables.GettingDataOutofARDB!ThedominantlanguageformanipulatingdatainrelationaldatabasesiscalledSQL,whichisshortforStructuredQueryLanguage.PronouncedsequelorEss-Que-EllSAShasawellimplementedversionofSQLandIuseit