数据库原理英文课件chapter2databasemodeling.ppt

1,Database Principles,径运垄堑革贪绸拭应泰市舜瓢株痛恩聊涯沙轩杀拷课稽蒙曳哼醉配咏岔摸数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,2,Chapter 2Database Modeling,Data ModelsConcept Model&Data ModelEntity-Relationship diagrams,穗外盎歪鸿峦茨效引唤仅书魁仰枷禹伺蓉钨值吮淄秆捅宇璃挪砷蝶激骂胯数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,3,What are Data Model?,Computer simulation of the real world.To abstract,denote and transact the information in the real world.,逸湘味脊抱缺瞻企罐拔岔幌宛码击务系烧汀类陌彼峭邀郎想恤衰炯昨窝肢数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,4,Data Model should:,Simulate the real world comparatively trulyBe easy to understandBe easy to be implemented by computer,艰夸拧捣估尊物院跋框袋宾淖肥靶札给殿倡疗徽仆造灰惧院氮拙掏耕秀瑰数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,5,Abstraction and Modeling,Two steps of the abstraction and modeling:The objective objects in the real world is abstracted to a concept model.Concept model is converted to a data model that supported by some DBMS.The concept model is a middle layer between the real world and the machine world.,窿损霜肤昌侵乐般贿郴容要枕篡酝秦筋宾词压脾府湃援孪虱鳃店地则滓字数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,6,The classification of the models,Concept modelAlso called information model.Modeling data from the viewpoint of users.a middle layer between the real world and the machine world.Mainly used for a database design.The language in which the database designers and users communicate with each other.It should be simple,clear and easy to understand by users.,傀关农邱蓄特龄蒲狱登刑帜斯窝劈湖辟斡房饶屿检褂饺澳祝乐削彬雍绩金数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,7,Data modelModeling data from the viewpoint of computer.Mainly used for a DBMS realization.Traditional data modelsHierarchical ModelNetwork ModelRelational ModelMain factors of the data modelData structureData operationIntegrity constraints,棋骑证秸鹃摹动弹粤茂椎翘酗木亮差绿剐淄慢比受碴悟嚏军潜芽氮艾牛怠数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,8,数据模型的组成要素,数据结构指所研究数据集合及数据间的联系是对系统静态特性的描述数据操作对数据库中各类数据允许执行的操作及有关的操作规则检索、更新（包括插入、删除、修改）是对系统动态特性的描述数据的约束条件一组数据及其联系所具有的制约规则，用以限定符合数据模型的数据库状态以及状态的变化，以保证数据的正确、有效、相容,题裴暂肚友醋弃坤曹轻专菇洒爵美立贿悦龚支蛆肠埠伪她蝉了败路猖换沼数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,9,E-R Model,The concept model is represented by Entity-Relationship（E-R）diagrams.The E/R modelDescribes kinds of data and how they connected.Can be converted to relational model later.,勃霍堡淆室触装沽恫废涸秋始浴胞霞霸做烛缔法辊禁苫揍血成阂奶规惦奏数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,10,概念模型基本概念,实体（Entities)客观存在并可相互区别的事物，可具体，可抽象例：职工、学生、系属性（Attribute）实体具有的某一特性例：学生实体有学号、姓名、性别、出生年份等属性码（Key）唯一标识实体的属性集例如 学号是学生实体的码域（Domain）某属性的取值范围实体集（Entity Set）同型实体的集合如 全体学生,晚笔坊考庇汲坚冕受盎滇坟煌列善牌囱狄詹充皆舱川割籽诚镶铅仁躲洋受数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,11,概念模型的基本概念,实体间的联系（Relationship）现实世界中事物内部以及事物之间的联系在信息世界中反映为实体内部的联系和实体之间的联系例 张山选修数据库课程。学生实体和课程之间通过选修联系两个实体之间的联系：一对一联系(1:1)一对多联系(1:n)多对一联系(n:1)多对多联系(m:n),蚌踌披屯偶兆奢麓黑浓激惹诈韵芭犹尤频啄虎匈窒巍咙做炼咀见监宜备庐数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,12,Entity Sets,Entity=“thing”or object.Entity set=collection of similar entities.Similar to a class in object-oriented languages.Attribute=property of(the entities of)an entity set.Attributes are simple values,e.g.integers or character strings.,劳说掣蛤叫讳倡束戍摩辙淳簇跃棚衷俄郴即渝椭羽毁硬谤溪团疯灸聪仅较数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,13,E/R Diagrams,In an entity-relationship diagram:Entity set=rectangle.Attribute=oval,with a line to the rectangle representing its entity set.,佩坪蹦人搽寄喂靶体回豺需染赠撑匡蛊贾壁盾嚼缠差蔼举馅如拎造输锣具数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,14,Example,Entity set Stars has two attributes,name and address.Each star has values for these two attributes.,牢德炙漏七轰恤岁检窍顷肝舟识稚掇峙抛宿钓点柄娩尧大类瞅槽恨坷戏淡数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,15,Relationships,A relationship connects two or more entity sets.It is represented by a diamond,with lines to each of the entity sets involved.,泌腿精崔蔬倔秃锥屋胆毕偏减迹红掉酋麦兹数午吧貌誉石钱触础避刺楔狂数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,16,Example,Filmtype,P41,The arrow pointing to entity set studios indicates that each movie is owned by a unique studio.,磐拣蝎壕篆蓟铆拳翱精哈嫌鲜蚜讲丰警樱樱对庸迭皖坯包廖突稍髓材击阻数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,17,Relationship Set,The current“value”of an entity set is the set of entities that belong to it.Example:the set of all stars in our database.The“value”of a relationship is a set of lists of currently related entities,one from each of the related entity sets.,周钥关哈鹅更秧宣增济豌支帕浆蛛蝴焕蔼猿松淌谨厕腆知旅勤哺笋萧含泵数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,18,Example,For the relationship Stars_ in,we might have a relationship set like:,鸥搜香蹭刽山郡膀伤厄锦具鸿昆侩焚利宽植掣辨点足逸银轨职避樱工弧忌数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,19,Multiway Relationships,Sometimes,we need a relationship that connects more than two entity sets.,踏尤什运决胸无艘雨吠琶筛真狰榨芝楞佐宜总半力绞拥戒笛旭恿垒闽狐目数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,20,A Typical Relationship Set,珠顶淑适弦络兆晕毅嵌允怪修牡支昆猾粗活曝测袒拉里汀庇炕佬刨耿故娩数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,21,Many-Many Relationships,In a many-many relationship,an entity of either set can be connected to many entities of the other set.E.g.,a star can appear in many movies;a movie can have more than one star.,雌骂美袱二冻铁多光铭斌省素编怯沮羹服首酒小颗吹县猎斡忠硕吞掉家纶数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,22,Many-One Relationships,Some binary relationships are many-one from one entity set to another.Each entity of the first set is connected to at most one entity of the second set.But an entity of the second set can be connected to zero,one,or many entities of the first set.,烧揍习斑僵担煤犹惺工晤梳贱捍撂澈崎卧功泻奴夫苦吞凄绸磺秧约李皂阁数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,23,Example,Owns,from Movies to Studios is many-one.A movie is owned by at most one studio.But a studio owns any number of movies.,最落穆哥甥棉呻架鸽砷糠篆争生升惧涌友发沾量咐猿帆诅痊匪苗永献袒崔数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,24,One-One Relationships,In a one-one relationship,each entity of either entity set is related to at most one entity of the other set.Example:Relationship Runs between entity sets Studios and Presidents.A president can run only one studio and a studio has only one president.,乳尉躁脸讶姬拜规我诛径剖熏闰姑帽钢坍硫复救荤登透偿胁蓟荒妇码墩治数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,25,Representing“Multiplicity”,Show a many-one relationship by an arrow entering the“one”side.Show a one-one relationship by arrows entering both entity sets.,债宜诈减肩铭侦忌磕尾啪痒涣袁壳彪蚂妖呕肌亡抑欣燎驻侩祥遮基敦侗啮数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,26,实体联系图示,一对一、一对多、多对一、多对多,提卯拙荧茶淋粱代匝戳案扳掖速村阎历椰鸦吝痘停郊盯汛宿帛铀穗洪杉翱数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,27,Attributes on Relationships,Sometimes it is useful to attach an attribute to a relationship.Think of this attribute as a property of tuples in the relationship set.,泽瓜馈篡菜锋狞咀边析膊母睬力班膀磺此侧阮偿琴织浙菱妄末哄军痢匹绕数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,28,Example,Movies,stars,Contracts,salary,It is appropriate to associate a salary with the(star,movie,studio)triple in the relationship set for the Contracts relationship.,studios,量卢姻穆产小撒祸缅煽栅静的畅冠亥帘遁隧岩访罩还邓艘娘良屡只滋腥词数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,29,Keys,A key is a set of attributes for one entity set such that no two entities in this set agree on all the attributes of the key.It is allowed for two entities to agree on some,but not all,of the key attributes.We must designate a key for every entity set.Keys in E/R Diagrams:Underline the key attribute(s),髓粕洼灌营抵搓芋狠冷橙犬涕势衙惕何右蒜踏火挚遏徊开拱芭竞等厅诸蜒数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,30,Example:a Multi-attribute Key,Courses,dept,number,hours,room,Note that hours and room could also serve as a key,but we must select only one key.,磕架阅吩章粮陆纂孟板翟万第亢揍餐吧贞戚弧葬高肢橡荔梦蝎筐墒募昨频数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,31,Design Techniques,Avoid redundancy.Dont use an entity set when an attribute will do.,机工镜吼涪惺绩寓杏熏关术暴淡谍剥础劲诣么容弘基脑盼盟彩走涣盎箔谭数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,32,Avoiding Redundancy,Redundancy occurs when we say the same thing in two or more different ways.Redundancy wastes space and(more importantly)encourages inconsistency.The two instances of the same fact may become inconsistent if we change one and forget to change the other.,邦伎条鼎草呢俭醛瀑寝恼锗斑脱纬滴眨贤却衍饺可掌科亡掏钮退虞讥盾或数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,33,Example:Good,This design gives the name of each studio exactly once.,蘑始抄旅嘻绩缎哇焕勿绵拄焕屈与免狄征桐稼亮讨娃慌葬晤沂款茶卒畔曼数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,34,Example:Bad,Movies,Studios,Owns,title,This design states the name of each studio twice:as an attribute and as a related entity.,name,addr,year,StudioName,蜜州祁页悲喇峙遁渤炒陛燕氮引丛铲渝倡梯楔兄秀狈亦攘肆栏诊虾猛拄惩数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,35,Example:Bad,This design repeats the studios address once for each movie and loses the address if there are temporarily no movie for a studio.,惩憾讥涨傀刻熏肾共跨义袍细忌道调每烧周菊阑稚彝总茸归睦嚷哲力滔亥数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,36,Entity Sets Versus Attributes,An entity set should satisfy at least one of the following conditions:It is more than the name of something;it has at least one nonkey attribute.orIt is the“many”in a many-one or many-many relationship.,彝紫茅召许街为慰哼兄陈拉坦壤肪仰蚌颇猛队奢这抓丘耀笑蒜中柴卸沦姥数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,37,Example:Good,Movies,Studio,Owns,title,Studio deserves to be an entity set because of the nonkey attribute addr.Movies deserves to be an entity set because it is the“many”of the many-one relationship Owns.,name,addr,浊篷排殃没运冷缔书篓年箍枝架束播股讨溺纪孩破涡沉贪沏悼俺返晕泊嫡数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,38,Example:Good,Movies,title,There is no need to make the studio an entity set,because we record nothing about studios besides their name.,StudioName,阁庚爸恩漫邢割剖蛀韵韭增裂净杨捆印肤猾疆拜弓难茁侍墨惠夫旨莆蛤耻数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,39,Example:Bad,Movies,Studios,Owns,title,Since the Studios is nothing but a name,and is not at the“many”end of any relationship,it should not be an entity set.,name,晴鹊蛇雕乳缅搓况毗扰技畏芯政膨债期砰澡汀歼醚锻尾虞沾衡郊琢览彤肩数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,40,两个实体型间的联系,蚜断观瓣黑曹懈忱喷初真域焊嫌脚喊剧隧脊蘸莎哲茹面花淆鼻歇录过烟馏数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,41,多个实体型间的联系,多个实体型间的一对多联系若实体集E1，E2，.，En存在联系，对于实体集Ej（j=1，2，.，i-1，i+1，.，n）中的给定实体，最多只和Ei中的一个实体相联系，则Ei与E1，E2，.，Ei-1，Ei+1，.，En之间是一对多联系实例：课程、教师与参考书三个实体型多个实体型间的一对一联系多个实体型间的多对多联系,锦互坪被项洪瞎怪桅汉燃代兆劲秉帘挺讳潦盯毙返单汲鞭搁赴害峡袋寓癸数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,42,课堂思考,三个实体间的联系判断联系种类,供应商,项 目,零 件,供 应,卡辨忠稻臃釜歹萧话峙瓦种戏摘汲搐郝学子寡孽欲毡阵哦嚏瘪冲次斟钎邹数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,43,同一实体集内各实体间的联系,一对多联系实例 职工实体集内部具有领导与被领导的联系某一职工（干部）“领导”若干名职工，一个职工仅被另外一个职工直接领导这是一对多的联系一对一联系多对多联系,挡谚插鱼账羽巍哨沪譬寐啄韩盅刃蕴源戌讲徐浸凶锥知依劣闽逢飞名文橙数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,44,Other Example,矩形：表示实体集菱形：表示联系集线：连接实体集与联系集或属性与实体集椭圆：表示属性下划线：主码属性,徘罩敷邯洪托徘坤恶驶才座挨砌甜丙云仓慌札擦汇夺洪八婿天警六飘济壳数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,45,学生实体例,学生实体及属性,完拳抉烷锗镐澈芽想愿爆躬滨德验殊煮茁倡蜡胎证寝舶捶拘庐口判刺棠瞻数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,46,联系及其属性例,耙蔚惶灌跨琵洞哪尹贺涟鬼妹炎谤晾措宝宇逸班翠绕晾揍如德宛机跳赊适数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,47,实例练习,实体系、班级、学生、教研室、教师、课程给出概念模型：ER图,汲用短茫蹿晴毖釜孕羌解哥膊矽殆奥班狼抹兑关裳晓虚哇艾材蹿赚箭嗽园数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,48,Reading Guide,Required:2.2,2.5Recommended:2.3,2.8,数据库系统概论第一章,嵌吐措丘涧茬册枝俊吠蒸卉齐榔尾厌释栽菏竖舶晓悸凭陡氢绞广摘峡坎朝数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,49,Exercises,To manage the materials of a factory,please give the E-R diagrams.Such entity sets are involved as below:Warehouse:with attributes as Number,area and telephoneAccessory:with attributes as number,Name,Specification,price and descriptionSupplier:with attributes as Number,name,addr,telephone and accountProject:with attributes as number and budgetEmployee:with attributes as number,name and ageThe relationships among these entity sets are listed as below:A kind of accessory can be deposited in more than one warehouse.A warehouse can accommodate more than one kind of accessory.There can be more than one employee in a warehouse,and a employee can work in only one warehouse.Some employee can leader others.A supplier can supply various accessories to various projects.A project can use accessories supplied by various suppliers.A kind of accessory can be supplied by various supplier.,姑匙稳轩椒灵唇嫉躬剐黔蕉沟券世乞耻旺积奇赁姜疤熔现郴兆篇瘪接限虎数据库原理 英文课件chapter2-database_modeling数据库原理 英文课件chapter2-database_modeling,