Lecture Database system concepts - Chapter 6: Entity relationship model

This chapter introduces the entity-relationship model in detail. The chapter covers numerous features of the model, several of which can be omitted depending on the planned coverage of the course. This chapter presents the following content: Design process, modeling, constraints, ER diagram, design issues,. | Chapter 6: Entity­Relationship Model Database System Concepts, 5th Ed. ©Silberschatz, Korth and Sudarshan See ­ for conditions on re­use Chapter 6: Entity­Relationship Model s Design Process s Modeling s Constraints s E­R Diagram s Design Issues s Weak Entity Sets s Extended E­R Features s Design of the Bank Database s Reduction to Relation Schemas s Database Design s UML Database System Concepts ­ 5th Edition, July 11, 2005 6. ©Silberschatz, Korth and Sudarshan Modeling s A database can be modeled as: q a collection of entities, q relationship among entities. s An entity is an object that exists and is distinguishable from other objects. q Example: specific person, company, event, plant s Entities have attributes q Example: people have names and addresses s An entity set is a set of entities of the same type that share the same properties. q Example: set of all persons, companies, trees, holidays Database System Concepts ­ 5th Edition, July 11, 2005 6. ©Silberschatz, Korth and Sudarshan Entity Sets customer and loan customer_id customer_ customer_ customer_ loan_ amount name street city number Database System Concepts ­ 5th Edition, July 11, 2005 6. ©Silberschatz, Korth and Sudarshan Relationship Sets s A relationship is an association among several entities Example: Hayes customer entity depositor relationship set A­102 account entity s .