数据库课程设计实验报告文档格式.docx
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数据库课程设计实验报告文档格式.docx
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王亮
谢明敏
学号
5040309458
班级
F0403016
F0403014
完成日期
2007/7/5
CONTENT
1.Introduction
Adatabasemanagementsystem(DBMS)iscomputersoftwaredesignedforthepurposeofmanagingdatabases.TypicalexamplesofDBMSsincludeOracle,DB2,MicrosoftAccess,MicrosoftSQLServer,Postgres,MySQLandFileMaker.DBMSsaretypicallyusedbyDatabaseadministratorsinthecreationofDatabasesystems.
ADBMSisacomplexsetofsoftwareprogramsthatcontrolstheorganization,storageandretrievalofdatainadatabase.ADBMSincludes:
1.Amodelinglanguagetodefinetheschema(relationalmodel)ofeachdatabasehostedintheDBMS,accordingtotheDBMSdatamodel.
●Thethreemostcommonorganizationsarethehierarchical,networkandrelationalmodels.Adatabasemanagementsystemmayprovideone,twoorallthreemethods.Invertedlistsandothermethodsarealsoused.Themostsuitablestructuredependsontheapplicationandonthetransactionrateandthenumberofinquiriesthatwillbemade.ThedominantmodelinusetodayistheadhoconeembeddedinSQL,acorruptionoftherelationalmodelbyviolatingseveralofitsfundamentalprinciples.ManyDBMSsalsosupporttheOpenDatabaseConnectivityAPIthatsupportsastandardwayforprogrammerstoaccesstheDBMS.
2.Datastructures(fields,recordsandfiles)optimizedtodealwithverylargeamountsofdatastoredonapermanentdatastoragedevice(whichimpliesveryslowaccesscomparedtovolatilemainmemory).
3.Adatabasequerylanguageandreportwritertoallowuserstointeractivelyinterrogatethedatabase,analyzeitsdataandupdateitaccordingtotheusersprivilegesondata.
●Italsocontrolsthesecurityofthedatabase.
●Datasecuritypreventsunauthorizedusersfromviewingorupdatingthedatabase.Usingpasswords,usersareallowedaccesstotheentiredatabaseorsubsetsofitcalledsubschemas.Forexample,anemployeedatabasecancontainallthedataaboutanindividualemployee,butonegroupofusersmaybeauthorizedtoviewonlypayrolldata,whileothersareallowedaccesstoonlyworkhistoryandmedicaldata.
●IftheDBMSprovidesawaytointeractivelyenterandupdatethedatabase,aswellasinterrogateit,thiscapabilityallowsformanagingpersonaldatabases.However,itmaynotleaveanaudittrailofactionsorprovidethekindsofcontrolsnecessaryinamulti-userorganization.Thesecontrolsareonlyavailablewhenasetofapplicationprogramsarecustomizedforeachdataentryandupdatingfunction.
4.Atransactionmechanism,thatideallywouldguaranteetheACIDproperties,inordertoensuredataintegrity,despiteconcurrentuseraccesses(concurrencycontrol),andfaults(faulttolerance).
●Italsomaintainstheintegrityofthedatainthedatabase.
●TheDBMScanmaintaintheintegrityofthedatabasebynotallowingmorethanoneusertoupdatethesamerecordatthesametime.TheDBMScanhelppreventduplicaterecordsviauniqueindexconstraints;
forexample,notwocustomerswiththesamecustomernumbers(keyfields)canbeenteredintothedatabase.SeeACIDpropertiesformoreinformation(Redundancyavoidance).
ThecomponentsofaDBMS:
TheDBMSacceptsrequestsfordatafromtheapplicationprogramandinstructstheoperatingsystemtotransfertheappropriatedata.
WhenaDBMSisused,informationsystemscanbechangedmuchmoreeasilyastheorganization'
sinformationrequirementschange.Newcategoriesofdatacanbeaddedtothedatabasewithoutdisruptiontotheexistingsystem.
OrganizationsmayuseonekindofDBMSfordailytransactionprocessingandthenmovethedetailontoanothercomputerthatusesanotherDBMSbettersuitedforrandominquiriesandanalysis.Overallsystemsdesigndecisionsareperformedbydataadministratorsandsystemsanalysts.Detaileddatabasedesignisperformedbydatabaseadministrators.
DatabaseserversarespeciallydesignedcomputersthatholdtheactualdatabasesandrunonlytheDBMSandrelatedsoftware.Databaseserversareusuallymultiprocessorcomputers,withRAIDdiskarraysusedforstablestorage.Connectedtooneormoreserversviaahigh-speedchannel,hardwaredatabaseacceleratorsarealsousedinlargevolumetransactionprocessingenvironments.
DBMS'
sarefoundattheheartofmostdatabaseapplications.SometimesDBMSsarebuiltaroundaprivatemultitaskingkernelwithbuilt-innetworkingsupportalthoughnowadaysthesefunctionsarelefttotheoperatingsystem.
FeaturesandAbilitiesofDBMS:
OnecancharacterizeaDBMSasan"
attributemanagementsystem"
whereattributesaresmallchunksofinformationthatdescribesomething.Forexample,"
color"
isanattributeofacar.Thevalueoftheattributemaybeacolorsuchas"
red"
"
blue"
silver"
etc.Latelydatabaseshavebeenmodifiedtoacceptlargeorunstructured(pre-digestedorpr
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