数据库 外文翻译 外文文献 英文文献 数据库管理系统的介绍

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1、AintroductiontoDatabaseManagementSystemRaghuRamakrishnanAdatabasesometimesspelleddatabaseisalsocalledanelectronicdatabasereferringtoanycollectionofdataorinformationthatisspeciallyorganizedforrapidsearchandretrievalbyacomputer.Databasesarestructuredtofacilitatethestorageretrievalmodificat

2、ionanddeletionofdatainconjunctionwithvariousdata-processingoperations.Databasescanbestoredonmagneticdiskortapeopticaldiskorsomeothersecondarystoragedevice.Adatabaseconsistsofafileorasetoffiles.Theinformationinthesefilesmaybebrokendownintorecordseachofwhichconsistsofoneormorefields.Fields

3、arethebasicunitsofdatastorageandeachfieldtypicallycontainsinformationpertainingtooneaspectorattributeoftheentitydescribedbythedatabase.Usingkeywordsandvarioussortingcommandsuserscanrapidlysearchrearrangegroupandselectthefieldsinmanyrecordstoretrieveorcreatereportsonparticularaggregateofd

4、ata.Complexdatarelationshipsandlinkagesmaybefoundinallbutthesimplestdatabases.ThesystemsoftwarepackagethathandlesthedifficulttasksassociatedwithcreatingaccessingandmaintainingdatabaserecordsiscalledadatabasemanagementsystemDBMS.TheprogramsinaDBMSpackageestablishaninterfacebetweenthedatab

5、aseitselfandtheusersofthedatabase..TheseusersmaybeapplicationsprogrammersmanagersandotherswithinformationneedsandvariousOSprograms.ADBMScanorganizeprocessandpresentselecteddataelementsformthedatabase.Thiscapabilityenablesdecisionmakerstosearchprobeandquerydatabasecontentsinordertoextract

6、answerstononrecurringandunplannedquestionsthataren’tavailableinregularreports.Thesequestionsmightinitiallybevagueand/orpoorlydefinedbutpeoplecan“browse”throughthedatabaseuntiltheyhavetheneededinformation.InshorttheDBMSwill“manage”thestoreddataitemsandassembletheneededitemsfromthecommonda

7、tabaseinresponsetothequeriesofthosewhoaren’tprogrammers.AdatabasemanagementsystemDBMSiscomposedofthreemajorparts:1astoragesubsystemthatstoresandretrievesdatainfiles2amodelingandmanipulationsubsystemthatprovidesthemeanswithwhichtoorganizethedataandtoadddeletemaintainandupd