associative entity

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Associative Entities It’s an entity Type – it has attributes AND it’s a relationship – it links entities together When should a relationship with attributes instead be an associative entity – All relationships for the associative entity should be many – The associative entity could have meaning independent of the other entities – The associative entity preferably has a unique identifier, and should also have other attributes – The associative may be participating in other relationships other than the entities of the associated relationship – Ternary relationships should be converted to associative entities.
An associative entity (CERTIFICATE) Associative entity involves a rectangle with a diamond inside. Note that the many-to-many cardinality symbols face toward the associative entity and not toward the other entities
Page 1 and 2: Data Processing AAOC C311 I Semeste
Page 3 and 4: Binary relationships
Page 5 and 6: Basic relationship with only maximu
Page 7 and 8: A binary relationship with an attri
Page 9 and 10: A unary relationship with an attrib
Page 11 and 12: Professors and courses (fixed upon
Page 13: Strong and weak entities Strong ent
Page 17 and 18: Ternary relationship as an associat
Page 19 and 20: ER - Example © Prentice Hall, 2002
Page 21: Next Lecture on …. Enhanced ER ER

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