Entity-Relationship Model
Overview
In this tutorial, we will learn about relational database design using Entity-Relationship Model. An Entity-Relationship Model is the most common used model for relational database design.
An Entity-Relationship Model is used to model a relational database using a top-down method. This method starts with an overall black box view, then adds detail as the process is refined. The product of this modelling process is a diagram called an Entity-Relationship Diagram (ERD).
Entities and Relationships
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ER Diagram
The outcome or the product of the database modelling process is a diagram called as an Entity-Relationship Diagram(ER Diagram or in short ERD ). The Entity-Relationship Diagram is a high-level graphical description of a data model. We can use this model diagram to assist in the database design.
There are multiple ERD types and are used at different stages of the database modelling. Popular ER model notations are as follows:
- Chen Model
- Crow’s Foot Model
- UML Model
Crow’s foot notation is one of the most intuitive ER diagram notation style.
Example
In this example, we will use the MySQL world database. The database consists of three tables.
- Country
- City
- CountryLanguage
MySQL world database ER Diagram
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