Entity Relationship Model in DBMS
Table of Content:
The Entity-Relationship Model is the most popular conceptual model used for designing a database. It was originally proposed by Dr Peter Chen in 1976 as a way to unify the network and relational database views. The E-R model views the real world as a set of basic objects (known as entities), their characteristics (known as attributes) and associations among these objects (known as relationships). The entities, attributes and relationships are the basic constructs of an E-R model.
Advantages of E-R model
- It is simple and easy to understand and, thus, can be used as an effective communication tool between the database designer and the end user.
- It captures the real-world data requirements in a simple, meaningful and logical way.
- It can be easily mapped to the relational model. The basic constructs, that is, the entities and attributes of the E-R model can be easily transformed into relations (or tables) and columns (or fields) in a relational model.
- It can be used as a design plan and can be implemented in any database management software.
Entity:
An entity is a distinguishable object that has an independent existence in the real world. It includes all those ‘things’ of an organization about which the data are collected. For example, each book, publisher and author in an Online Book database is an entity. An entity can exist either physically or conceptually.
Tangible entity:
If an entity has a physical existence, it is termed as tangible or concrete entity. For example, a book, an employee, a place or a part.
Non-tangible:
If an entity has a conceptual existence, it is termed as non-tangible or abstract entity. For example, an event, a job title or a customer account.