ENTITY RELATIONSHIP MODEL

Contents:

I. Introduction

II.The building blocks: entities, relationships, and attributeso  Entity o Entity seto Attributes seto Attributes Typeso Relationship Seto Relationship Type

III. SUMMARY OF ER-DIAGRAM NOTATION FOR ER SCHEMASIV. University ER Diagram

The ER model:

• The E-R model consider the real world consisting of a basic object.

• It is expressed in terms of entities in the business environment, the relationships among those entities and the attributes (properties) of both the entities and their relationships.

• There are 3 basic notification –Entities and Entity SetAttribute SetRelationship Set

• Entity- An entity is “thing” or “object” in a real world that is distinguishable from all other object.

• Entity Set – An entity set is a set of entities of same type that share the same properties or attributes.

• Attribute Set-

An entity is represented by set of attributes.

Attributes may also be associated with relationships

• Types of Attribute

Single Attribute- Composed of single component

Composite Attribute- Composed of multiple component

Single Valued Attribute- Single valued for single entity

Multi valued Attribute- Multiple values for single entity

Drive Attribute- Derived from the value of related attribute

• Relationship Set-

Relationship between two entities and attributes

• Types of Relationship:

1:1 Relationship

1:M Relationship

M:M Relationship

SUMMARY OF ER-DIAGRAM NOTATION FOR ER SCHEMAS

University ER Diagram