What is an ER model in DBMS?

ER model stands for the Entity Relationship Model in the database management system (DBMS). It is the first step of designing to give the flow for a concept and is the DFD (Data Flow Diagram) requirement of a company.

It is the basic building block for relational models. Not that much training is required to design the database project. It is very easy to convert the E-R model into relational tables or to normalize tables.

It is a high-level data model diagram that defines the conceptual view of the database. It acts as a blueprint to implement a database in future.

Features of ER model

The features of the ER model are as follows −

  • It is widely used to develop the initial design of the database.

  • It provides a collection of basic concepts that can be easily implemented in a database system.

  • It describes data as a set of entities, attributes, and relationships.

  • It provides the graphical view of the database design.

Basic constraints

The basic constraints for the ER model are as follows −

  • Entities

  • Entity set

  • Degree of relationship

  • Connectivity or cardinality

  • Direction

Steps for designing ER-model

Step 1 − Identify the entities from the given database.

Step 2 − Find relationships among entities.

Step 3 − Identify the key attribute for every entity.

Step 4 − Identify the other relevant attribute.

Step 5 − Draw the complete E-R diagram with all the attributes including primary key.

Step 6 − Review your results according to the requirements of the database.

Entity relationship diagram is the graphical representation of entities and relationships among those entities in the database.


The advantages of the ER model are as follows −

  • It is easy to create and understand.

  • It is very simple because if you know the relationship between attributes and entities, you can easily draw it.

  • It is a tool for effective communication for database designers.

  • It can be easily converted into a Relational Model


The disadvantages of the ER model are as follows −

  • It is not suitable for the semi-structured or unstructured data set.

  • It is difficult to show data manipulation.