Entity Relationship Diagram: Role and How to Draw an ERD Model

Entity Relationship Diagram an increasing number of businesses have been focusing on creating. This model gives businesses a broader view of their sales management database system, allowing them to develop practical business plans. In this article, Viindoo will provide you with fundamental information on the ERD model that businesses can refer to.

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What is an Entity Relationship Diagram? History of the ERD model

An Entity Relationship Diagram (ERD) also known as the Entity-Relationship model, is a type of structure commonly used in designing databases. ERD contains symbols to visually connect different important information: the main entities in the system and the relationships between them.

Entity Relationship DiagramEntity Relationship Diagram

The concept of ERD was first found in ancient Greece with the works of Aristotle, Socrates, and Plato. The ERD model continued to be found in the works of logicians like Charles Sanders Peirce and Gottlob Frege in the 19th and 20th centuries. In the 1970s, this concept was further developed by Professor Peter Chen.

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What is the role of the Entity Relationship Diagram model in sales management?

The ERD model for sales management plays an important role in any business, especially for commercial enterprises, in sales management. Here are some roles of the ERD diagram for sales management:

  • Database design: The ERP model is used to design the information database diagram in the business.
  • Troubleshooting database issues: The ERD diagram is applied to analyze the current database system to identify and resolve issues and problems that arise in the business's data system.
  • Systematize business processes: The ERD model helps businesses rationalize their business processes and improve organizational operations.
  • Business process reengineering (BPR): The ERD diagram helps businesses analyze their database. From there, they can restructure their business processes and establish a new database.
  • Research: The ERD model plays an important role in establishing useful databases, and businesses can analyze this data to serve their production and business operations.
Entity Relationship Diagram
ERD plays an important role in businesses

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How to draw an Entity Relationship Diagram model for sales management

Before drawing an ERD diagram, we need to understand each component that makes up the diagram in detail. Specifically:


An entity (also known as an object, event, etc.) in ERD is a person, object, event, etc. that is identified and can be stored in a data system. For example students, customers, cars, products, etc. In ERD models, an entity is represented as a rectangle with rounded corners, with the name at the top and attributes listed in the body.

Entity Attributes

This concept is also called the attributes of the entity. Attributes have a descriptive name and type, for example, varchar for a string and int for an integer. Attributes are represented in the ERD system by an oval shape.

Primary Key

Also known as PK or primary key. The primary key is a unique type of entity attribute in the database table. In other words, there cannot be two (or more) primary keys. The primary key is also represented by an oval shape like an attribute but with a horizontal line underneath.

Entity Relationship DiagramHow to draw an ERD diagram

Foreign Key

A foreign key (abbreviated as FK) refers to the primary key in a table. The foreign key is used to identify relationships between entities. There may be many foreign keys in an ERD diagram. Many record tables can share the same data type.


The relationship represents how two entities are linked. For example, an employee working for a company. The two entities here are employees and companies. The relationship is the work activity that connects the two entities. Diamond shapes often represent relationships or directly attach to the connecting lines between the two entities.


Determines the number of relationships between two or more entities. The three main relationships are one-to-one, one-to-many, and many-to-many. For example, an employee will be linked to a unique contact phone number (one-to-one). A department may have multiple employees (one-to-many). Employees in a company have relationships with many different managers. And managers are also linked to many employees (many-to-many). In the ERD diagram, cardinality is represented as a bird's footprint at the ends of the connectors.

Therefore, to draw an ERD diagram, we need to pay attention to the following special symbols:

  • A rectangle shape represents entities, with each shape representing an entity.
  • An oval shape represents attributes, with the attribute name written inside the oval.
  • A rhombus shape represents relationships.

The basic steps to draw ERD diagram for sales management include:

  • Identify entities by listing and selecting information based on documents and prepared records,
  • Determine the relationship constraints between entities and attributes,
  • Determine the possible relationships between entities and combined relationships,
  • Draw the ERD model using geometric symbols and then prepare, condense, and rearrange the diagram.
Entity Relationship Diagram

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Describes the quantitative characteristics of the connection between two entities or sets of entities. The different types include one-to-one, one-to-many, and many-to-many relationships.

Yes, ERDs can serve as a blueprint for generating a database schema.

Yes, ERDs can be used to model relationships in both relational and non-relational databases.

Through this article, Viindoo has compiled basic information on the Entity Relationship Diagram for businesses. We hope this article will be helpful and assist your business in building a suitable ERD model for your organization.

Entity Relationship Diagram: Role and How to Draw an ERD Model
Viindoo Technology Joint Stock Company, Amber Nguyen March 16, 2023

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