ch6 - Database System Concepts, 5th Ed . Silberschatz,...

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Unformatted text preview: Database System Concepts, 5th Ed . Silberschatz, Korth and Sudarshan See www.db-book.com for conditions on re-use Chapter 6: Entity-Relationship Model Chapter 6: Entity-Relationship Model Silberschatz, Korth and Sudarshan 6.<number> Database System Concepts - 5 th Edition, July 11, 2005 Chapter 6: Entity-Relationship Model Chapter 6: Entity-Relationship Model Design Process Modeling Constraints E-R Diagram Design Issues Weak Entity Sets Extended E-R Features Design of the Bank Database Reduction to Relation Schemas Database Design UML Silberschatz, Korth and Sudarshan 6.<number> Database System Concepts - 5 th Edition, July 11, 2005 Modeling Modeling A database can be modeled as: a collection of entities, relationship among entities. An entity is an object that exists and is distinguishable from other objects. Example: specific person, company, event, plant Entities have attributes Example: people have names and addresses An entity set is a set of entities of the same type that share the same properties. Example: set of all persons, companies, trees, holidays Silberschatz, Korth and Sudarshan 6.<number> Database System Concepts - 5 th Edition, July 11, 2005 Entity Sets Entity Sets customer customer and and loan loan customer_id customer_ customer_ customer_ loan_ amount name street city number Silberschatz, Korth and Sudarshan 6.<number> Database System Concepts - 5 th Edition, July 11, 2005 Relationship Sets Relationship Sets A relationship is an association among several entities Example: Hayes depositor A-102 customer entity relationship set account entity A relationship set is a mathematical relation among n 2 entities, each taken from entity sets {( e 1 , e 2 , e n ) | e 1 E 1 , e 2 E 2 , , e n E n } where ( e 1 , e 2 , , e n ) is a relationship Example: (Hayes, A-102) depositor Silberschatz, Korth and Sudarshan 6.<number> Database System Concepts - 5 th Edition, July 11, 2005 Relationship Set Relationship Set borrower borrower Silberschatz, Korth and Sudarshan 6.<number> Database System Concepts - 5 th Edition, July 11, 2005 Relationship Sets (Cont.) Relationship Sets (Cont.) An attribute can also be property of a relationship set....
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This note was uploaded on 04/28/2010 for the course CSE cse123 taught by Professor Benny during the Spring '10 term at LSU Eunice.

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ch6 - Database System Concepts, 5th Ed . Silberschatz,...

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