Entity Relational model

Entity-Relationship Model

Introduction

An Entity-Relationship Model (ERM) is a conceptual data model that describes the structure of a database using entities, attributes, and relationships.

Components

• Entities: Objects or concepts that have independent existence, such as customers, orders, or products.
• Attributes: Characteristics or properties of entities, such as customer name, order date, or product price.
• Relationships: Connections between entities, such as a customer placing an order or a product being part of an order.

Relationship Types

• One-to-One (1:1): One entity is related to only one other entity.
• One-to-Many (1:N): One entity is related to multiple other entities.
• Many-to-Many (M:N): Multiple entities are related to multiple other entities.

Benefits

• Improved Communication: ERMs help stakeholders understand data requirements and relationships.
• Better Data Design: ERMs guide the design of databases and ensure data consistency.
• Reduced Data Redundancy: ERMs help identify and eliminate data redundancy.

Notation

• Entity-Relationship Diagrams (ERDs): Visual representations of ERMs, using entities, attributes, and relationships.
• Crow's Foot Notation: A popular notation for ERDs, using crow's feet to represent relationships.