SQL数据库-毕业外文翻译

SQL数据库-毕业外文翻译

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1、WorkingwithDatabasesThischapterdescribeshowtouseSQLstatementsinembeddedapplicationstocontroldatabases.Therearethreedatabasestatementsthatsetupandopendatabasesforaccess:SETDATABASEdeclaresadatabasehandle,associatesthehandlewithanactualdatabasefile,andopt

2、ionallyassignsoperationalparametersforthedatabase.SETNAMESoptionallyspecifiesthecharactersetaclientapplicationusesforCHAR,VARCHAR,andtextBlobdata.Theserverusesthisinformationtotransliteratefromadatabase’sdefaultcharactersettotheclient’scharactersetonSEL

3、ECToperations,andtotransliteratefromaclientapplication’scharactersettothedatabasecharactersetonINSERTandUPDATEoperations.gCONNECTopensadatabase,allocatessystemresourcesforit,andoptionallyassignsoperationalparametersforthedatabase.Alldatabasesmustbeclose

4、dbeforeaprogramends.AdatabasecanbeclosedbyusingDISCONNECT,orbyappendingtheRELEASEoptiontothefinalCOMMITorROLLBACKinaprogram.DeclaringadatabaseBeforeadatabasecanbeopenedandusedinaprogram,itmustfirstbedeclaredwithSETDATABASEto:CHAPTER3WORKINGWITHDATABASES

5、.Establishadatabasehandle.Associatethedatabasehandlewithadatabasefilestoredonalocalorremotenode.Adatabasehandleisaunique,abbreviatedaliasforanactualdatabasename.DatabasehandlesareusedinsubsequentCONNECT,COMMITRELEASE,andROLLBACKRELEASEstatementstospecif

6、ywhichdatabasestheyshouldaffect.ExceptindynamicSQL(DSQL)applications,databasehandlescanalsobeusedinsidetransactionblockstoqualify,ordifferentiate,tablenameswhentwoormoreopendatabasescontainidenticallynamedtables.Eachdatabasehandlemustbeuniqueamongallvar

7、iablesusedinaprogram.Databasehandlescannotduplicatehost-languagereservedwords,andcannotbeInterBasereservedwords.Thefollowingstatementillustratesasimpledatabasedeclaration:EXECSQLSETDATABASEDB1=’employee.gdb’;Thisdatabasedeclarationidentifiesthedatabasef

8、ile,employee.gdb,asadatabasetheprogramuses,andassignsthedatabaseahandle,oralias,DB1.Ifaprogramrunsinadirectorydifferentfromthedirectorythatcontainsthedatabasefile,thenthefilenamespecificationinSETDATABASEmustincludeafullpathname,

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