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It explains the roles of entity sets, relationship sets, and common E-R diagram notations using rectangles, diamonds, lines, and attribute ellipses, including multivalued and derived attributes. The chapter also covers entity set fundamentals, attribute types and domains, relationship roles, and mapping cardinalities for one-to-one, one-to-many, many-to-one, and many-to-many constraints with examples like customers and loans.",{"@graph":69,"@context":122},[70,84,105],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":30,"@type":76,"position":81},"https://docshare.wps.com/document/technology/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/chapter-2-entity-relationship-model-2-introduction-and-e-r-diagram-concepts/656099/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/chapter-2-entity-relationship-model-2-introduction-and-e-r-diagram-concepts/656099.png","ImageObject",300,407,{"name":92,"@type":93},"OKfine","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-11-02","2026-10-25",true,{"@type":102,"interactionType":103,"userInteractionCount":29},"InteractionCounter",{"@type":104},"ViewAction",{"@type":106,"mainEntity":107},"FAQPage",[108,114,118],{"name":109,"@type":110,"acceptedAnswer":111},"What is the purpose of the E-R model in database design?","Question",{"text":112,"@type":113},"The E-R model provides a way to model entities and the relationships among them to support database schema design.","Answer",{"name":115,"@type":110,"acceptedAnswer":116},"Which symbols are used in an E-R diagram for entity sets, relationship sets, and attributes?",{"text":117,"@type":113},"Rectangles represent entity sets, diamonds represent relationship sets, and ellipses represent attributes; derived attributes use dashed ellipses and multivalued attributes use double ellipses.",{"name":119,"@type":110,"acceptedAnswer":120},"How do mapping cardinalities define relationship constraints?",{"text":121,"@type":113},"Mapping cardinalities express how many entities can be associated through a relationship set, including one-to-one, one-to-many, many-to-one, and many-to-many constraints, often shown with directed or undirected lines.","https://schema.org",{"og:url":83,"og:type":124,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":126,"canonical":83},"index,follow",{"doc_id":128,"site_id":62},656099,1793052273,{"code":4,"msg":5,"data":131},{"doc_id":128,"user_id":132,"nickname":92,"user_avatar":133,"doc_module":4,"category_id":29,"category_name":30,"doc_title":65,"doc_description":67,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":29,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":139,"language":140,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":141,"faqs":142,"seo_title":143,"seo_description":67,"update_tm":144,"read_time":145},962093957596,"https://ap-avatar.wpscdn.com/davatar_29158cc5080c5b710cf443261637dec0","| \u003Cbr>Chapter 2: Entity-Relationship Model |\n| --- |\n| 􀂄􀂄􀂄􀂄􀂄􀂄􀂄􀂄􀂄􀂄\u003Cbr>What’s the use of the E-R model?\u003Cbr>Entity Sets Relationship Sets Design Issues Mapping Constraints Keys\u003Cbr>E-R Diagram Extended E-R Features\u003Cbr>Design of an E-R Database Schema Reduction of an E-R Schema to Tables\u003Cbr>\u003Cbr>\u003Cbr>\u003Cbr>\u003Cbr>\u003Cbr>Database System Concepts 2.1 ©Silberschatz, Korth and Sudarshan |\n\n\n| \u003Cbr>\u003Cbr>|  | E-R | Diagrams |  |  |  |\n| --- | --- | --- | --- | --- | --- | --- |\n|  |  |  |  |  |  |  |\n| |  |  |  |  |  |  |\n| \u003Cbr>\u003Cbr>􀂄 Rectangles represent entity sets.\u003Cbr>􀂄 Diamonds represent relationship sets.\u003Cbr>􀂄 Lines link attributes to entity sets and entity sets to relationship sets.\u003Cbr>􀂄 Ellipses represent attributes\u003Cbr>􀂄 Double ellipses represent multivalued attributes.\u003Cbr>􀂄 Dashed ellipses denote derived attributes. ~~ ~~ ~~ ~~\u003Cbr>􀂄 Underline indicates primary key attributes (will study later)\u003Cbr>\u003Cbr>\u003Cbr>Database System Concepts 2.2 ©Silberschatz, Korth and Sudarshan |  |  |  |  |  |  |\n\n| \u003Cbr>Attributes |\n| --- |\n| 􀂄 An entity is represented by a set of attributes, that is descriptive properties possessed by all members of an entity set.\u003Cbr>Example:\u003Cbr>customer = (customer-id, customer-name, customer-street, customer-city)\u003Cbr>loan = (loan-number, amount)\u003Cbr>􀂄 Domain – the set of permitted values for each attribute\u003Cbr>􀂄 Attribute types:\u003Cbr>􀂾 Simple and composite attributes.\u003Cbr>􀂾 Single-valued and multi-valued attributes\u003Cbr>􀃎 E.g. multivalued attribute: phone-numbers\u003Cbr>􀂾 Derived attributes\u003Cbr>􀃎 Can be computed from other attributes\u003Cbr>􀃎 E.g. age, given date of birth\u003Cbr>\u003Cbr>\u003Cbr>\u003Cbr>\u003Cbr>\u003Cbr>Database System Concepts 2.3 ©Silberschatz, Korth and Sudarshan |\n\n\n| \u003Cbr>Entity Sets |\n| --- |\n| 􀂄 A database can be modeled as:\u003Cbr>􀂾 a collection of entities,\u003Cbr>􀂾 relationship among entities.\u003Cbr>􀂄 An entity is an object that exists and is distinguishable from other objects.\u003Cbr>Example: specific person, company, event, plant\u003Cbr>􀂄 Entities have attributes\u003Cbr>Example: people have names and addresses\u003Cbr>􀂄 An entity set is a set of entities of the same type that share the same properties.\u003Cbr>\u003Cbr>\u003Cbr>\u003Cbr>\u003Cbr>\u003Cbr>Database System Concepts 2.4 ©Silberschatz, Korth and Sudarshan\u003Cbr>Example: set of all persons, companies, trees, holidays |\n\n| Relationship Sets with Attributes\u003Cbr>|\n| --- |\n| |\n| \u003Cbr>\u003Cbr>\u003Cbr>\u003Cbr>\u003Cbr>Database System Concepts 2.5 ©Silberschatz, Korth and Sudarshan |\n\nE-R Diagram With Composite, Multivalued, and Derived Attributes—try to avoid them  \nDatabase System Concepts 2.6 ©Silberschatz, Korth and Sudarshan  \n| Composite Attributes |\n| --- |\n|  |\n| \u003Cbr>\u003Cbr>\u003Cbr>\u003Cbr>\u003Cbr>\u003Cbr>Database System Concepts 2.7 ©Silberschatz, Korth and Sudarshan |\n\n| \u003Cbr>\u003Cbr>|  |  |  | Roles |  |  |  |  |\n| --- | --- | --- | --- | --- | --- | --- | --- | --- |\n|  |  |  |  |  |  |  |  |  |\n| 􀂄 Entity sets of a relationship need not be distinct\u003Cbr>􀂄 The labels “manager” and “worker” are called roles ; they specify how employee entities interact via the works-for relationship set.\u003Cbr>􀂄 Roles are indicated in E-R diagrams by labeling the lines that connect diamonds to rectangles.\u003Cbr>􀂄 Role labels are optional, and are used to clarify semantics of the relationship\u003Cbr>\u003Cbr>\u003Cbr>\u003Cbr>\u003Cbr>\u003Cbr>Database System Concepts 2.8 ©Silberschatz, Korth and Sudarshan |  |  |  |  |  |  |  |  |\n\n| \u003Cbr>Mapping Cardinalities |\n| --- |\n| 􀂄 Express the number of entities to which another entity can be associated via a relationship set.\u003Cbr>􀂄 Most useful in describing binary relationship sets.\u003Cbr>􀂄 For a binary relationship set the mapping cardinality must be one of the following types:\u003Cbr>􀂾 One to one\u003Cbr>􀂾 One to many\u003Cbr>􀂾 Many to one\u003Cbr>􀂾 Many to many\u003Cbr>\u003Cbr>\u003Cbr>\u003Cbr>\u003Cbr>\u003Cbr>Database System Concepts 2.9 ©Silberschatz, Korth and Sudarshan |\n\nMapping Cardinalities  \nOne to one One to many  \nNote: Some elements in A and B may not be mapped to any elements in the other set  \nDatabase System Concepts 2.10 ©Silberschatz, Korth and Sudarshan  \nMapping Cardinalities  \nMany to one Many to many  \nNote: Some element","cbCaisbY90s4USkX","https://ap.wps.com/l/cbCaisbY90s4USkX","pdf",1597063,26,"English","# What’s the use of the E-R model?\n## E-R Diagram Notation and Features\n## Attributes and Domains\n## Entity Sets\n## Relationship Sets and Roles\n## Mapping Cardinalities","[{\"question\":\"What is the purpose of the E-R model in database design?\",\"answer\":\"The E-R model provides a way to model entities and the relationships among them to support database schema design.\"},{\"question\":\"Which symbols are used in an E-R diagram for entity sets, relationship sets, and attributes?\",\"answer\":\"Rectangles represent entity sets, diamonds represent relationship sets, and ellipses represent attributes; derived attributes use dashed ellipses and multivalued attributes use double ellipses.\"},{\"question\":\"How do mapping cardinalities define relationship constraints?\",\"answer\":\"Mapping cardinalities express how many entities can be associated through a relationship set, including one-to-one, one-to-many, many-to-one, and many-to-many constraints, often shown with directed or undirected lines.\"}]","Chapter 2: Entity-Relationship Model - 2 - Introduction and E-R Diagram Concepts | PDF",1792966316,66]