个人财务管理系统的设计与实现外文资料及翻译Word格式.docx

个人财务管理系统的设计与实现外文资料及翻译Word格式.docx

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Database（sometimesspelleddatabase）isalsocalledanelectronicdatabase,referringtoanycollectionsofdata,orinformation,thatisspeciallyorganizedforrapidsearchandretrievalbyacomputer.Databasesarestructuredtofacilitatethestorage，retrievalmodificationanddeletionofdatainconjunctionwithvariousdata—processingoperations。

Databasecanbestoredonmagneticdiskortape，opticaldisk,orsomeothersecondarystoragedevice。

Adatabaseconsistsofafileorasetoffiles。

Theinformationinthethesefilesmaybebrokendownintorecords，eachofwhichconsistsofoneormorefieldsarethebasicunitsofdatastorage，andeachfieldtypicallycontainsinformationpertainingtooneaspectorattributeoftheentitydescribedbythedatabase。

Usingkeywordsandvarioussortingcommands,userscanrapidlysearch，rearrange,group，andselectthefieldsinmanyrecordstoretrieveorcreatereportsonparticularaggregatesofdata。

Databaserecordsandfilesmustbeorganizedtoallowretrievaloftheinformation.Earlysystemwerearrangedsequentially（i.e.,alphabetically，numerically,orchronologically）；

thedevelopmentofdirect-accessstoragedevicesmadepossiblerandomaccesstodataviaindexes.Queriesarethemainwayusersretrievedatabaseinformation.Typicallytheuserprovidesastringofcharacters，andthecomputersearchesthedatabaseforacorrespondingsequenceandprovidesthesourcematerialsinwhichthosecharactersappear。

Ausercanrequest，forexample,allrecordsinwhichthecontentofthefieldforaperson’slastnameisthewordSmith。

Themanyusersofalargedatabasemustbeabletomanipulatetheinformationwithinitquicklyatanygiventime。

Moreover，largebusinessandotherorganizationstendtobuildupmanyindependentfilescontainingrelatedandevenoverlappingdata，andtheirdata，processingactivitiesoftenrequirethelinkingofdatafromseveralfiles.Severaldifferenttypesofdatabasemanagementsystemshavebeendevelopedtosupporttheserequirements：

flat,hierarchical，network,relational,andobject-oriented。

Inflatdatabases，recordsareorganizedaccordingtoasimplelistofentities；

manysimpledatabasesforpersonalcomputersareflatinstructure.Therecordsinhierarchicaldatabasesareorganizedinatreelikestructure，witheachlevelofrecordsbranchingoffintoasetofsmallercategories.Unlikehierarchicaldatabases,whichprovidesinglelinksbetweensetsofrecordsatdifferentlevels,networkdatabasescreatemultiplelinkagesbetweensetsbyplacinglinks，orpointers，toonesetofrecordsinanother；

thespeedandversatilityofnetworkdatabaseshaveledtotheirwideuseinbusiness.Relationaldatabasesareusedwhereassociationsamongfilesorrecordscannotbeexpressedbylinks;

asimpleflatlistbecomesonetable，or“relation”，andmultiplerelationscanbemathematicallyassociatedtoyielddesiredinformation.Object—orienteddatabasesstoreandmanipulatemorecomplexdatastructures,called“objects"

whichareorganizedintohierarchicalclassesthatmayinheritpropertiesfromclasseshigherinthechain；

thisdatabasestructureisthemostflexibleandadaptable。

Theinformationinmanydatabasesconsistsofnatural—languagetextsofdocuments；

number—orienteddatabaseprimarilycontaininformationsuchasstatistics,tables，financialdata，andrawscientificandtechnicaldata.Smalldatabasescanbemaintainedonpersonal-computersystemsandmaybeusedbyindividualsathome.Theseandlargerdatabaseshavebecomeincreasinglyimportantinbusinesslife.Typicalcommercialapplicationsincludeairlinereservations，productionmanagement,medicalrecordsinhospitals,andlegalrecordsofinsurancecompanies.Thelargestdatabasesareusuallymaintainedbygovernmentalagencies，businessorganizations,anduniversities.Thesedatabasesmaycontaintextsofsuchmaterialsascatalogsofvariouskinds。

Referencedatabasescontainbibliographiesorindexesthatserveasguidestothelocationofinformationinbooks，periodicals，andotherpublishedliterature。

Thousandsofthesepubliclyaccessibledatabasesnowexist，coveringtopicsrangingfromlaw，medicine，andengineeringtonewsandcurrentevents,games，classifiedadvertisements，andinstructionalcourses.Professionalssuchasscientists，doctors，lawyers,financialanalysts，stockbrokers,andresearchersofalltypesincreasinglyrelyonthesedatabasesforquick，selectiveaccesstolargevolumesofinformation.

DBMSStructuringTechniques

Sequential,direct，andotherfileprocessingapproachesareusedtoorganizeandstructuredatainsinglefiles。

ButaDBMSisabletointegratedataelementsfromseveralfilestoanswerspecificuserinquiriesforinformation。

Thatis，theDBM