Entity- Relationship model (chapter-05)

Headings

• ER concept and terminology.
• Entities, Relationship and attribute.
• ER Diagrams.
• Mapping conceptual model into relational schema.
• Introduction to ERR modelling
• ER concept and terminology.
• Entities, Relationship and attribute.
• ER Diagrams.
• Mapping conceptual model into relational schema.
• Introduction to ERR modelling
• ER concept and terminology.

ER concept and terminology.

• The basic building blocks of all data models are 

1. Entities
2. Attributes
3. Relationships
4. Constraints                 

Entities

• An entity represents a particular type of object the real world.
• An entity is"distinguishable"_ that is ,each entity occurrence is unique and distinct.
• An entity is a person,place,thing,or event about which data will be collected and stored. For example ,                                          
  a CUSTOMER entity would have many distinguishable customer occurrences, such as John Smith, Pedro Dinamita , and Tom Strickland.

• Entities may be physical objects,such as customers or products,but entities may also be abstractions,such as flight routes or musical concerts.

Attribute

• An attribute is a characteristic of an entity .
•