ERwin使用說明(中英文)

1、GettingStartedwithERwin（Erwin入門）byDr.PeterWolcottDepartmentofInformationSystemsandQuantitativeAnalysisCollegeofInformationScienceandTechnologyUniversityofNebraskaatOmaha（由內(nèi)布拉斯加州的奧馬哈大學(xué)信息科學(xué)與技術(shù)學(xué)院門的信息系統(tǒng)和定量分析博士彼得著）Introduction（介紹）EFWinisapopulardatamodelingtoolusedbyanumberofmajorcompaniesinOmahaandthrou

2、ghouttheworld。（Erwin是受奧馬哈和世界各地的一些主要的公司歡迎的數(shù)據(jù)模型工具）Theproductiscurrentlyowned,developed,andmarketedbyComputerAssociates,aleadingsoftwaredeveloper0（該產(chǎn)品是由具有領(lǐng)導(dǎo)地位的CA軟件開發(fā)公司擁有、開發(fā)和銷售）Theproductsupportsavarietyofaspectsofdatabasedesign,includingdatamodeling,forwardengineering（thecreationofadatabaseschemaandphy

3、sicaldatabaseonthebasisofadatamodel）,andreverseengineering（thecreationofadatamodelonthebasisofanexistingdatabase）forawidevarietyofrelationalDBMS,includingMicrosoftAccess,Oracle,DB2,Sybase,andothers.該軟件為多種多樣的關(guān)系型數(shù)據(jù)庫管理系統(tǒng)，包括MicrosoftAccess,甲骨文，Sybase,DB?和其他人提供支持?jǐn)?shù)據(jù)庫設(shè)計(jì)的各個(gè)方面，包括數(shù)據(jù)建模、正向工程（在現(xiàn)有的數(shù)據(jù)模型的基礎(chǔ)上創(chuàng)建數(shù)據(jù)模式和

4、物理數(shù)據(jù)庫）和逆向工程（在現(xiàn)在的數(shù)據(jù)庫基礎(chǔ)上創(chuàng)建數(shù)據(jù)模型）ThisbrieftutorialstepsyouthroughtheprocessofcreatingadatamodelusingERwin.（你可以通過這個(gè)簡單教程中的步驟運(yùn)用Erwin來創(chuàng)建數(shù)據(jù)模型）ItwillnotexplainallaspectsofERwin,butwillshowyoutheminimumnecessarytocreateandusedatamodelsforthisclass.（這個(gè)課程不可能全面地講解Erwin,但它向你展示了必要的最基本的創(chuàng)建和使用數(shù)據(jù)模型的知識）Itconsistsofthree

5、majorsegments,whichcorrespondtotheprojectrelatedassignmentsinyourclass:（這個(gè)課程由三個(gè)主要部分組成，它與有關(guān)項(xiàng)目任務(wù)相符）1. Creationofabasicdatamodel（Conceptualdatamodel）創(chuàng)建一個(gè)基本的數(shù)據(jù)模型（概念數(shù)據(jù)模型）2. Creationofadatabaseschema建立數(shù)據(jù)庫模式3. Creationofthedatabase創(chuàng)建數(shù)據(jù)庫Thistutorialisastaticone,suitableforprinting。本教程是一個(gè)靜態(tài)的,適合印刷Atutorialusi

6、ngscreencapturesandnarrationisalsoavailable。一個(gè)指南使用屏幕捕捉和敘述是可用的。Section1.CreationofabasicdatamodelYouwillbecreatingadatamodelsimilartothatcreatedfortheHeartlandPropertiescasestudyusedinclass.教程中你將創(chuàng)建一個(gè)和研究心臟地帶個(gè)案相似的數(shù)據(jù)模型TheEntitiesinvolvedinthismodelinclude:Employee,Office,Property,andInspection。參與本次的實(shí)體模型

7、包括：員工、辦公、財(cái)產(chǎn)、及檢驗(yàn)。First,invokeERwinfromStart-ProgramsComputerAssociates-AllFusion-ERwinDataModeler>Erwin首先，從開始-程序-CA-所有程序-ERwinDataModelerYouwillfirstencounteradialogboxentitled“ModelMartConnectionManager"（經(jīng)理ModelMart連接）.SimplyclickonCancel。將首先遇到一個(gè)對話框題為“ModelMartConnectionManager".只需點(diǎn)擊“取消

8、"。Youwillbeaskedtochoosebetweencreatinganewmodel,andopeninganexistingmodel,asshowninFigure1你將被要求之間作出選擇，創(chuàng)造了一種新的模式，開放個(gè)現(xiàn)有的模型，如圖1所示。Forthisexercise,createanewmodel.通過這個(gè)練習(xí)，創(chuàng)建一個(gè)新的模型Figure1:CreateanewmodelThenextdialogbox,showninFigure2,willaskyoutochoosethetemplatetobeusedtocreatethenewmodel。下一個(gè)對話框，如

9、圖2所示，會讓你選擇的模板可以被用來創(chuàng)造新的模型Atthispoint,youmayassociatethemodelwithatargetDBMroduct,suchasMicrosoftAccess,Oracle,DBZetc。在這一點(diǎn)上，你可以把這個(gè)模型與如MicrosoftAccess,甲骨文,DB2等目標(biāo)數(shù)據(jù)庫產(chǎn)品聯(lián)系在一起Youwillhavetheopportunitytochangethischoicelater,butfornowchooseMicrosoftAccess。你之后將有機(jī)會改變這種選擇，但是現(xiàn)在選擇MicrosoftAccessoAlso,chooseLogic

10、al/Physicalasthenewmodeltype。同時(shí)，選擇的邏輯或者物理彳為新模型形式Thischoicewillallowustoswitchbackandfortheasilybetweenalogicalmodel(ERDiagram)andaphysicalmodel(databaseschema).這個(gè)選擇將讓我們輕易之間來回切換邏輯模型(ER圖)和物理模型(資料庫)Figure2:SelectingamodeltypeERwinwillnowdisplaythemainwindowfromwhichmostofyourERdiagramdevelopmentwillbed

11、one,asshowninFigure3.ERwin現(xiàn)在將顯示在主窗口大部分你ER圖發(fā)展來完成，如圖3。' Computer Asoci dies ERivin - Model 1 : <Mapn Subject Area ：= / Displd y 1|n|_x際FMEditViewFormatModalModef4artTookWindowHetU<91X口空口|8|黝"l耳甲©虱我錢口|04|LogicaljJJ時(shí)晶J弊直網(wǎng)-3厄三JI上皿I、：港府金角金.日011tli1QOOoaT1-'蟀i+E20orpins_J理WodelSourc

12、es”ValidationRuleswDehukValues可TiansfwmsQEntitiesEfSubjectAreasFigure 3: The ERwin Workplace ERwin工作場所TheERwinworkplaceconsistsoftwomainparts.OntheleftistheModelNavigator,whichdisplaysahierarchyofitemsofimportance,suchasentities,domains,andsubjectareas.左面是模型的領(lǐng)航員，顯示某層次的物品的重要性，如實(shí)體、領(lǐng)域和課題。Ontherightisth

13、eDisplayWindowwhichwillshowtheERdiagramitself。右邊是顯示窗口，它能夠顯示ER圖本身Asyoucreateobjects,theywillappearinthedisplaywindow(iftheyarevisualinnature,likeentities),andappearinthehierarchywithintheModelNavigator.當(dāng)你創(chuàng)建對象時(shí)，他們將會出現(xiàn)在顯示器窗口(如果它們是視覺的自然屬性，就像實(shí)體)，并將出現(xiàn)在層級模型導(dǎo)航器.SettingPreferences偏好設(shè)置AtoollikeERwincanaccomod

14、ateanumberofdatamodelingnotationsandconventions。像ER這樣工具可以容納大量的數(shù)據(jù)建模的符號和對話Inmyclasspleasemakethefollowingchangestothepreferencesbeforeyoubegintocreateyourmodel在我的課上請完成下面的改變的偏好，在你開始之前，創(chuàng)造你的模型：1. FromtheFormat>EntityDisplaymenu,makesurethatPrimaryKeyDesignatorischecked從格式>實(shí)體顯示菜單，確保主鍵欄進(jìn)行檢查2. Fromthe

15、Format-EntityDisplaymenu,makesurethatForeignKeyDesignator(FK)isunchecked0從格式-實(shí)體顯示菜單，確保外國關(guān)鍵指示器(FK)是不能檢查3. FromtheFormat>EntityDisplaymenu,makesurethatShowMigratedAttributesisunchecked.從格式>實(shí)體顯示菜單，確保顯示屬性遷移至ijunchecked4. FromtheFormat->RelationshipDisplay,makesurethatVerbPhraseischecked.從格式一關(guān)系顯

16、示、確保動詞短語進(jìn)行檢查Inaddition,youmaychoosebetweentwodifferentERdiagrammingnotations。另外，你可以選擇兩種不同的e-r種畫圖符號InERwin,clickonModel-ModelPropertiestoseethewindowshowninFigure3b:點(diǎn)擊模型一>窗口模型屬性看到如圖3b。ModelProperties6ensralDefinitionnotationDefaultsIHIDeFaullsUDFHistoryOptior>sHistoryLogicalNotationIDEF1X0rtegr

17、ationDEFinitianfoiInfermatianModelrgj衣IEInforntionEngineeringPhysicalHalation-IDEF11(IntegrationDEFinidonfofInformationModeling)"遮PnformafieriErigineeringl0K(DmenaonalModeling)CancelFigure3b:Choiceofnotation("Crows Foot ”)notation. You may also use IDEF1X,if you wish 。本教程是基于信息工程（"烏鴉腳”

18、）的符號你也可以使用IDEF1X,如果你愿意的話。Creating an Entity創(chuàng)造一個(gè)實(shí)體To create a new entity,click on theentity icon ()on the toolbar ,ThistutorialisbasedontheInformationEngineering創(chuàng)建一個(gè)新orrightclickonthewordEntityintheModelNavigator。的實(shí)體，點(diǎn)擊實(shí)體工具欄上的圖標(biāo)（）,或者以右鍵點(diǎn)擊這個(gè)詞中的實(shí)體模型導(dǎo)航器Ifyouclickontheentityicon,youthenshouldclickonthe,a

19、s shown inDisplayWindowwhereyouwouldliketheentitytoappearD om-ains Model 5 ources Validation Rule6 Default Values T rdnforms Entities SubieclA(eas冽 File Edit View Format Model ModeMaft Tools 刷indow Help Computer rtssoci ales ER win - Model I * ; <Main Subject Area? f Displ aylFigure 4.如果你點(diǎn)擊了實(shí)體圖標(biāo)，

20、那么你應(yīng)該點(diǎn)擊顯示窗口，在那里你會喜歡 這個(gè)實(shí)體出現(xiàn)的各位朋友，如圖4所示.Lx|4| x田廣：；：一；田：由ill& MdelR Su.Q c*o.后朝dpFigure4：AnewentityNoticethatthedefaultnamefortheentityisE/x，wherexissomenumber（2inthiscase）。注意，默認(rèn)的名字因?yàn)閷?shí)體是E/x,那里的x是一些數(shù)字（2在這種情況下）ClickontheTabkeyseveraltimesandnoticewhathappens。點(diǎn)擊Tab鍵了好幾次，通知會發(fā)生些什么Pressingthetabkeycause

21、thefocustocyclebetweenthethreemainpartsoftheEntity:按tab鍵引起關(guān)注焦點(diǎn),周期之間的三個(gè)主要部分的實(shí)體thenameoftheentity,theprimarykeyattribute（s）主要的關(guān)鍵屬性，andthenon-primarykeyattribute（s）時(shí)速的關(guān)鍵屬性（s）.Ingeneral，tomodifyoneofthesethreepartsoftheentity，youwillpresstheTabkeytocycletotheappropriatepartoftheentity，thentypetoaddormod

22、ifythatpartoftheentity。一般來說，修改這三部分的實(shí)&你會按Tab鍵循環(huán)到適寸的一部分，然后輸入實(shí)體的增加或修改的那部分實(shí)體Rightnow，presstheTabkeyuntiltheentitynameishighlighted.現(xiàn)在，按Tab鍵，直到實(shí)體名稱是突出了ThentypeEMPLOYEEisshowninFigure5。然后輸入雇員，如圖5.Figure5:ChangingthenameoftheentityAtthispoint,youmaywishtosaveandnameyourdiagramtoavoidlossshouldthesystem

23、orapplicationcrash.在這一點(diǎn)上，你可能想要存起來，說出你的圖來避免損失應(yīng)該系統(tǒng)或應(yīng)用程序崩潰.Addingprimarykeycolumns添力主鍵字段OnceyouhavechangedthenametoEMPLOYEE：,presstheTabkeyagaintomovethefocustothenextpartoftheEntity,addingaprimarykeyattribute。一旦你已經(jīng)更改了名稱給員工，按Tab鍵來移動焦點(diǎn)再下一部分的實(shí)體,添力個(gè)關(guān)鍵屬性Thentypethenameoftheprimarykeyattribute,Emp_Num,assho

24、wninFigure6。然后輸入名稱的屬性，Emp_Numt鍵，如圖6.Figure6:AddingaprimarykeyattributeNoticethatbecauseofthepreferencesyousetearlier,theprimarykeyattributehasakeyiconnexttoit。值得注意的是，因?yàn)槟愕南埠迷O(shè)定早些時(shí)候，主鍵的屬性是一個(gè)關(guān)鍵的圖標(biāo)旁邊。PresstheTabkeyonemoretimetobringthefocusbelowthehorizontallineintheEntity,whereyouwilladdinanumberofnon-p

25、rimarykeyattributes。按Tab鍵遍把焦點(diǎn)的水平線以下的實(shí)體，在那里您將加入一定數(shù)量的時(shí)速關(guān)鍵屬性。TypeEmp_Fnam|easshowninFigure7.Emp_Fnamffi,如圖7WhenyouhavetypedEmp_NamepresstheEnterkey(notTab)當(dāng)你打了Emp_Name按回車鍵(不是選項(xiàng)卡)。Noticewhathappens當(dāng)你學(xué)得。ThecursorisnowpositionedforyoutoaddanotherattributeinthissameportionoftheEntity,thenon-primarykeyattri

26、buteportion。定位光標(biāo)被現(xiàn)在你添加另一個(gè)屬性在這個(gè)相同的部分實(shí)體、時(shí)速關(guān)鍵屬性分.Figure7:AddingnonprimarykeyattributesContinueaddingthefollowingnonprimarykeyattributes:繼續(xù)增力口下列時(shí)速關(guān)鍵屬性:Emp_LnameEmp_SSNEmp_StreetEmp_CityEmp_StateEmp_ZipcodeEmp_PhoneEmp_FaxYourdiagramshouldnowlooklikeFigure8Figure8:TheEmployeeentityRepeattheentitycreation

27、processfortheentitiesandattributeslistedinTable1。重復(fù)這個(gè)實(shí)體創(chuàng)建過程中為實(shí)體及其屬性列于表1。EntityAttributesEntityAttributesOFFICEOffice_Num(pk)Office_StreetOffice_CityOffice_StateOffice_ZipcodeOffice_NameOffice_PhoneOffice_FaxINSPECTIOInsp_Date(pk)Insp_CommentsPROPERYProp_ID(pk)MANAGERMan_SalaryProp_StreetProp_CityPro

28、p_StateProp_TypeProp_BathsProp_RoomsPropMonthlyRentMan CarASSOCIATEAssocHourlyRateTable1:EntitiesandAttributesNoticethatsomeoftheentitieshavenoprimarykeyattributes(Manager,Associate),andoneentityhasanattributewhichispartoftheprimarykey,butbyitselfdoesnotconstituteaprimarykey(Inspection)。注意到一些實(shí)體屬性沒有主

29、鍵(經(jīng)理、副)，和一個(gè)實(shí)體有一個(gè)屬性的一部分，而是由主鍵本身并不會構(gòu)成一個(gè)主鍵(檢驗(yàn))oAsweaddrelationshipstothediagram,thenatureofthekeysfortheseentitieswillbecomeclear。當(dāng)我們添加關(guān)系圖，大自然的鑰匙，這些實(shí)體就變得清晰了Forthetimebeing,besurethattherearenoprimarykeyattributesforManagerandAssociate,andonlyoneprimarykeyattributeforInspection,asshowninFigure9.隨著時(shí)間的推移，

30、要確保沒有關(guān)鍵屬性對經(jīng)理及員工，只有一個(gè)主要的關(guān)鍵屬性進(jìn)行檢驗(yàn)，如圖9所示，Lumputer Associates ERwin - TUTORIALER Is* ： <Mair> Subject Area> / Di鈍場File Edit Wew Format Model ModdP4arE Tools Window HelpJn| X ,|g| XpFFlCE 喝口片足電Murn,! U曲.包住步D orruinsModel S ources Validation Rules Dehuk Values T rarpsfwm?Entities Subject AreasEm

31、pFname Emp_Ln舊 e電 Emp_SSN Emp_Gtrfi*t Emp.Ci 句 Em p_Staie Emp ipcoda EmpFhQFfce £mp_Q 'E 前WYEE a Emp_NumINSPECTIONin5p_DateMAWAERASSOCIATEMjr)_SaljryMdnCdr AllswjneeAw6C_Hi url_RateA ModelW Su.ispIcStrtei OfllwZcityQltlc< _Z>wde 口怖cjHam也 OfflM_PhdrTe 0-HIm F axPROPERTYProp_Gtreet Picp

32、_Cit)K Propw State Prop.Zipcode Prop Type FQp_ Baths PropRflQmsF Pirop_M onthlyRentidRedyAccessFigure9:HeartlandPropertiesEntitiesCreatingRelationships建立人際關(guān)系EFWinsupportsthecreationofrelationshipswiththreebasickindsofconnectivity(EFWin支持創(chuàng)造之間的關(guān)系三種基本的連通性：oneto-one,one-tomanyandmanyto-many。Withintheone

33、tomanycategory,ERwinallowsustodistinguishbetweenidentifyingandnon-identifyingone-tomanyrelationships。這對范疇，ithin歐文允許我們區(qū)分識別和nonidentifying一對多的關(guān)系.OnetomanyRelationshipsWellbeginwithtworelationships,betweenInspectionandEmployeeandbetweenInspectionandProperty。我們可以先開始兩個(gè)關(guān)系，檢驗(yàn)和員工之問，檢驗(yàn)和財(cái)產(chǎn)的權(quán)利之間Inspectionisrel

34、atedtobothPropertyandEmployee in one to many relationships同時(shí)與檢驗(yàn)是財(cái)產(chǎn)和員工在一對多的關(guān)系EachInspectionisundertakenatoneProperty;在進(jìn)行每個(gè)檢查是套房產(chǎn)eachPropertymayundergomanyinspections每處房產(chǎn)，可能經(jīng)過許多檢查。EachInspectioniscarriedoutbyoneEmployee每次檢驗(yàn)進(jìn)行了一名員工；eachEmployeecarriesoutmanyInspections每一位員工進(jìn)行許多檢查.Aretheserelationshipsi

35、dentifyingrelationshipsornon-identifyingrelationships?這些是關(guān)系識別關(guān)系或nonidentifying關(guān)系嗎？Aretheserelationshipsidentifyingrelationshipsornonidentifyingrelationships?這些是關(guān)系識另關(guān)系或nonidentifying關(guān)系嗎？TheissuehingesonthenatureoftheprimarykeyofInspection,theentityonthe“manysideoftherelationship。問題的關(guān)鍵在于性質(zhì)的主鍵的檢驗(yàn)、實(shí)體上的“

36、許多”方面的關(guān)系。TheprimarykeyofInspectioninthisexampleisacompositeprimarykeyconsistingoftwoattributes主鍵的檢驗(yàn)在本例中是一個(gè)合成物，主鍵由兩個(gè)屬性：Insp_Date,Prop_IDThebusinessruleineffecthereisthateachpropertyhasatmostoneinspectionperdayInsp_DateProp_ID的商業(yè)規(guī)則,在這里，每一種性質(zhì)影響的條件下，在大多數(shù)人檢查每天。Onemightarguewhetherornotthatisasoundassumpt

37、ion,butletssupposeforthesakeofillustrationthatitis。一個(gè)人可能會爭辯說不管那是一種合理的假設(shè)，但為了說明我們可以假設(shè)它是.NoticethattheprimarykeyofInspectionincludestheprimarykeyofProperty,theentitywithwhichithasarelationship.值得注意的是，主鍵檢查包括主鍵的性質(zhì)、實(shí)體與它有關(guān)系Forthisreason,wesaythattherelationshipbetweenInspectionandPropertyisanidentifyingone

38、to-manyrelationship.因?yàn)檫@個(gè)原因，我們說，檢驗(yàn)和財(cái)產(chǎn)之間的關(guān)系是一種識別一對多的關(guān)系。Anidentifyingrelationshipiscreatedbyclickingfirstontheidentifyingrelationshipicon(").創(chuàng)建一個(gè)識別關(guān)系是通過點(diǎn)擊第一的在識別關(guān)系圖標(biāo)()Noticethatithasthecrow'sfootnotation(indicating"many")andasolidline(indicatingidentifying)。值得注意的是，它有烏鴉腳的符號(表示“許多”)和一個(gè)實(shí)

39、線(指著識別)Tocreateanidentifyingrelationship,clickfirstonthisicon,thenclickontheparententity(ontheonesideoftherelationship)andthenclickonthechildentity(onthemanysideoftherelationship)。倉I建個(gè)識別關(guān)系，點(diǎn)擊先在這個(gè)圖標(biāo)，然后點(diǎn)擊“家長實(shí)體(在這邊的關(guān)系)，然后點(diǎn)擊孩子實(shí)體(在許多一端的關(guān)系)Inthiscase,youwillclickfirstontheidentifyingrelationshipicon,theno

40、nProperty,thenonInspection.在這種情況下，你就會點(diǎn)擊圖標(biāo)先識別，然后在產(chǎn)權(quán)關(guān)系，然后在檢查TheresultsareshowninFigure10.結(jié)果顯示于圖10Figure10:AnidentifyingrelationshipNoticethatERvinhasprovidedalabel"R/1"fortherelationship,whichisnotveryhelpful。值得注意的是，ERwin已經(jīng)提供了一個(gè)標(biāo)簽”R/1"的關(guān)系,而不是很有幫助Double-clickontherelationshipitselftobrin

41、gupadialogboxinwhichwecanfurtherrefinetherelationshipdefinition雙擊關(guān)系本身造就了一個(gè)對話框，以這種方式我們能夠進(jìn)一步提煉的關(guān)系的定義。FilloutthisdialogboxasshowninFigure11.填寫這對話框如圖11分Figure11:RelationshipsdefinitionIntheRelationship:textboxtherelationshipispresentedintheformparententityR/1childentity.在這段關(guān)系的關(guān)系：文本框的形式給出了R/1孩子家長實(shí)體的實(shí)體The

42、VerbPhraseportionofthisboxallowsustodefinethelabeltoplaceontherelationshipinplaceofR/1.這個(gè)動詞短語的一部分，這盒允許我們來定義標(biāo)簽的地方的關(guān)系上所處的R/1SincetheparententityisPropertyandtheChildentityisInspection,theParenttoChildverbphrasewillread“PropertyUndergoesInspection.”自從父母實(shí)體是財(cái)產(chǎn)和孩子的主體是檢查、Parent-toChild動詞短語會讀”財(cái)產(chǎn)經(jīng)歷檢查."T

43、heChildtoParentverbphrasewillread”InspectionUndertakenatProperty。"動詞短語的Child一to-Parent會讀”的檢測在進(jìn)行財(cái)產(chǎn)?！盜ntheRelationshipCardinalityportionofthiswindow,wecandeterminehowmanychildentityoccurencesmaybeassociatedwitheachparententityoccurence.人際關(guān)系的行集數(shù)的一部分，這窗戶,我們可以決定了有多少孩子實(shí)體檢測儀可伴有每個(gè)父母實(shí)體發(fā)生Morespecifically

44、,"OnePropertyUndergoesZero,OneorMoreInspections.”更具體地說，“一個(gè)財(cái)產(chǎn)經(jīng)歷零,一個(gè)或更多的檢查.”Noticethatatthispointwearealsoabletodefineparticipation.值得注意的是，在這一點(diǎn)上我們也能夠定義的參與。Ifeachpropertyhadtohaveundergoneatleastoneinspectioninordertobestoredinthedatabase,thenwecouldhaveforcedmandatoryparticipationbychoosingtheOne

45、orMoreoption。如果每個(gè)貝才產(chǎn)不得不經(jīng)歷了至少一個(gè)檢測為了被儲存在數(shù)據(jù)庫中，那么,我們就可以迫使強(qiáng)制性參與挑選一個(gè)或更多的選擇.ClickOKtocompletetherelationshipdefinition,asshowninFigure12。點(diǎn)擊OK完成關(guān)系定義，如圖12。Figure12:FinishedrelationshipNoticethatwhenanentityparticipatesasthechildinanidentifyingrelationshipitismodeledwithroundedcorners.值得注意的是,當(dāng)個(gè)實(shí)體作為識別的關(guān)系那孩子是模仿

46、和圓角。Thisnotationisusedforwhatinotherdatamodelingtoolsiscalleda”WeakEntity"。這個(gè)符號是用來在其他數(shù)據(jù)建模工具，一種被稱為“弱單位”。TherelationshipbetweenInspectionandEmployeeissomewhatdifferent。檢查和員工之間的關(guān)系是有不同的.Itisaone-tomanyrelationship,butitisnonidentifying,becausetheprimarykeyofEmployeeisnotpartoftheprimarykeyofInspect

47、ion.這是個(gè)對多的關(guān)系，但它是nonidentifying中的主鍵，因?yàn)楣蛦T沒有部分的主鍵檢查Forsucharelationship,wemustclickonthenonidentifyingrelationshipiconJ、（，），whichusesadashedlineinsteadofasolidline。對于這樣一個(gè)關(guān)系，我們必須點(diǎn)擊屏幕上的圖標(biāo)（：），它使用一個(gè)虛線來代替一個(gè)實(shí)線。Asbefore,weclickontheicon,thentheparententity,thenthechildentity。和以前一樣，我們點(diǎn)擊這個(gè)圖標(biāo)，那么父的實(shí)體，然后孩子的實(shí)體Click

48、onthenon-identifyingrelationshipicon,thentheEmployeeentity,thentheInspectionentity.點(diǎn)擊屏幕上的圖標(biāo),然后nonidentifying員工關(guān)系實(shí)體，然后檢驗(yàn)實(shí)體Double-clickontherelationshiptobringuptherelationshipdefinitionwindowandfillitinasshowninFigure13.oubleclick的關(guān)系來定義窗口和關(guān)系把它填上如圖13歲。Figure 13 : Non-identifying relationship definitio

49、noAsbefore，weprovidemoremeaningfulverbphrasesfortherelationship.和以前一樣，我們提供更多的有意義的動詞短語的關(guān)系A(chǔ)sbefore,sinceeachemployeemaybeassociatedwithzero,oneormoreinspections，wechoosethecorrespondingcardinality。和以前一樣，因?yàn)槊總€(gè)員工可能伴有零,一個(gè)或多個(gè)檢查，我們選擇相應(yīng)的行集數(shù)Unlikebefore，whenwechosetheidentifyingrelationshiptype，wehavenowchose

50、nthenonidentifyingrelationshiptype。不同于以往的，當(dāng)我們選擇了識別關(guān)系類型，我們現(xiàn)在已經(jīng)選好了nonidentifying關(guān)系類型.Wehavetheoptionofindicatingwhethernullsarepermittedornot。我們可以選擇是否允許nulls表示。Thisdecisionregardstheparticipationoftheparententityinarelationshipwiththechildentity。這一決定將參與實(shí)體的父母與孩子的關(guān)系實(shí)體。Inotherwords，doeseachchildentityocc

51、urence(Inspection)havetobeassociatedwithaparententityoccurence(Employee)？換句話說,每一個(gè)孩子的實(shí)體(檢查)發(fā)生有助于家長實(shí)體發(fā)生(雇員)嗎？Inthiscase，theansweryes。Eachinspectionmustbecarriedoutbyanemployee，oritisnotconsideredaproperinspection.在這種情況下,答案是的.每項(xiàng)考核必須執(zhí)行一個(gè)雇員,或并不被認(rèn)為是一個(gè)適當(dāng)?shù)臋z驗(yàn)。TheparticipationofEmployeeintherelationshipismand

52、atory。在參與的員工之間的關(guān)系是強(qiáng)制性的.ClickOKtocompletetherelationshipdefinition,asshowninFigure14.點(diǎn)擊OK完成關(guān)系定義，如圖14。,ln| x創(chuàng)座。& ® M 午呻窣 R觀以蚊囪士 Logical的晶需攝|tal刁b y u Ti空柏士修士D omins Model Sources Validation Rules Default Values T rarafo(mis E ntities G object Areas器 ModelR Su.Q g.irri" itit i srd亡t outFh

53、鄒匚GEE凸MSEtVlFLOYEEErnf>_NumEmpFname EinpLri ame Emp_SSN Em_ Street Einp=Cit Emp_ Slate Einp_Zipcode EmpPlhone Em& Fm靈IM5PE 匚 T【ONlfi5P_DateUrid巨用 UndeitASSOCIATEMjr)_S3ljryMan l且I Allov'ianGepmcE嗎 口ffi收 NumIcStrtei OfllwZcity Office _Z>wde 口怖cjHam也 OfflM_PhdrTe Off it* F axPROPERTYProp

54、_Gtreet Picp_Cit)K Prop_ Sta-te Prpp_Zipffldt FTop Type FQp_ Baths PQp_Rwm£ Pirop_M onthlyRent小03h eid、Computer酉號so口dtE，ERwin-TUTORIALER1=*：<MainSubjectArea>/Display1引'FiteEditViewFormatModelModdP4arEToolsWindowHelpR6dyAcces?Figure14:NonidentifyingrelationshipEmployeeandOfficealsopart

55、icipationinarelationshipwitheachother。員工和辦公室也參與相互認(rèn)識EachEmployeeisassignedtooneandonlyoneOffice,andeachOfficehasoneormoreEmployees。每個(gè)員工被指定至U唯一的一間辦公室，每個(gè)辦公室都擁有一個(gè)或更多的員工。Inthisonetomanyrelationship,OfficeistheparentandEmployeeisthechild.在這一對多的關(guān)系，辦公室是家長和員工是孩子。Sincetheprimarykeyofthechild(Employee)doesnoti

56、ncludetheprimarykeyoftheparent(Office),thisisanonidentifyingrelationship。自從主鍵的孩子(雇員)并不包括主鍵的父母(辦公室)，這是一個(gè)nonidentifying關(guān)系。Clickonthenonidentifyingrelationshipicon,Office,andEmployeetocreatethisrelationship.點(diǎn)擊屏幕上的圖標(biāo)non-identifying關(guān)系、寫字樓及員工，形成了這種關(guān)系。Double-clickontherelationshipandf川intherelationshipdefi

57、nitionwindowasshowninFigure15。雙擊關(guān)系并填入關(guān)系定義窗口如圖15。Figure15:AnonidentifyingrelationshipwithmandatoryparticipationInFigure15,seeanexampleofarelationshipinwhichparticipationismandatoryforbothentities。在圖15,看一個(gè)例子，這樣一種關(guān)系，參與對雙方都是強(qiáng)制性的實(shí)體TheCardinalityindicatesthateachOfficeisassociatedwithOneorMore(butnotZero)Employees。每間辦公室的行集數(shù)表明，伴隨著一個(gè)或多個(gè)(但不是零)的雇員.TheRelationshipTypeindicatesthatthisisanon-identifyingrelationship,andthatNullsarenotpermitted.他的關(guān)系類型顯示，這是一個(gè)non-identifying關(guān)系，Nul