note2-er - 1 CSc 134 Database Management and File...

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Unformatted text preview: 1 CSc 134 Database Management and File Organization 2. Entity-Relationship Model Ying Jin Computer Science Department California state University, Sacramento 2 Database Design Requirement Analysis Conceptual Design Logic Design Physical Design 3 Entity-Relationship Model Conceptual Model Entity, Relationship ER Diagram 4 Entity and Attribute Entity An object with a physical existence or conceptual existence e.g. a person, a company Notation Attributes Properties that describe entities e.g. Name of an employee Notation 5 Attribute- Simple vs. Composite attribute Simple (atomic) attribute Attribute that are not divisible e.g. SSN, ZIP code Notation Composite Attribute can be divided into smaller subparts e.g. Address Notation 6 Attribute- Single value vs. Multivaled attribute Single-valued attribute e.g. Age of a person Multivalued attribute e.g. College degree Notation 7 Attribute- Stored vs. Derived attribute Stored attribute e.g. birthDate Derived attribute Derived from other attribute e.g. age = current date birthDate Notation 8 Entity types and entity sets Entity Type Defines a collection of entities that have the same attributes. e.g. employee describe the schema or intension for a set of entities that share the same structure....
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note2-er - 1 CSc 134 Database Management and File...

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