er_diag - Entity-Relationship Model [ER Model] OUTLINE ER...

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Entity-Relationship Model [ER Model]
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OUTLINE b ER Model Concepts s Entities and Attributes s Entity Types, Value Sets, and Key Attributes s Relationships and Relationship Types s Weak Entity Types s Roles and Attributes in Relationship Types b ER Diagrams - Notation b ER Diagram for COMPANY Schema
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ER MODEL b Entity-Relational model is a popular high level conceptual data model and is used for conceptual design of database applications b E-R facilitate database design by representing overall logical structure of a database by specifying the properties of the data. b E-R data model employs three basic notions : s Entity sets s Relationship s Attributes b The E-R model is usually expressed as an E-R diagram
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Entities and Attributes b An entity is a thing or an object in the miniworld that are represented in databases. s Entity has set of properties and values . s Eg: Employee, Department, Person. b Attributes: Properties used to describe the entity. s EMPLOYEE Entity has four attributes Name, Address, Age, Phone. b Each entity has a value for each of its attributes . s Eg: Name=‘JONES’, Address=‘Harrington Road’,Age=40,Phone=01- 44-3470727
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Entity and Attributes Two entities Employee and Company and their attributes
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Types of Attributes b Attributes can be s composite / simple (atomic) s single-valued / multivalued s stored / derived s key / nonkey.
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Types of Attributes b Simple : Attribute that has a single atomic value or not divisible. s Example: SSN. b Composite : The attribute that can be divided into smaller subparts. s Example: Address (Apt#, House#, Street, City, State, ZipCode, Country) .
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Types of Attributes s Single Valued : Attributes with single value for a particular entity.
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This note was uploaded on 04/01/2012 for the course CSE,IT 101 taught by Professor Mirunaalini during the Spring '12 term at Indian Institute of Technology, Chennai.

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er_diag - Entity-Relationship Model [ER Model] OUTLINE ER...

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