Entity Relationship Diagram (ERD)

By Chidiere Oluoma

(Freepik, 2020)


Biscobing defines Entity Relationship Diagram (ERD) as "a graphical representation that depicts relationships among people, objects, places, concepts or events within an information technology (IT) system. An ERD uses data modeling techniques that can help define business processes and serve as the foundation for a relational database." (Biscobing, 2019)

The ERD comprises of certain terminologies used in relation to the items on the diagram. These are:

  • Entity

"An entity may be any object, class, person or place. In the ER diagram, an entity can be represented as rectangles. 
Consider an organization as an example- manager, product, employee, department etc. can be taken as an entity." (Javapoint, no date)
  • Attribute
"The attribute is used to describe the property of an entity. Eclipse is used to represent an attribute.
For example, id, age, contact number, name, etc. can be attributes of a student." (Javapoint, no date)
  • Relationship
The relationship "is used to describe the relation between entities. Diamond or rhombus is used to represent the relationship." (Javapoint, no date)

  • Cardinality

"Cardinality defines the possible number of occurrences in one entity which is associated with the number of occurrences in another. For example, ONE team has MANY players. When present in an ERD, the entity Team and Player are inter-connected with a one-to-many relationship." (Visual-paradigm, 2022)
This could be one-to-one, one-to-many, many-to-one, or many-to-many.

Importance of Entity Relationship Diagram (ERD) and its application

"Entity relationship diagrams provide a visual starting point for database design that can also be used to help determine information system requirements throughout an organization. After a relational database is rolled out, an ERD can still serve as a reference point, should any debugging or business process re-engineering be needed later.

However, while an ERD can be useful for organizing data that can be represented by a relational structure, it can't sufficiently represent semi-structured or unstructured data. It's also unlikely to be helpful on its own in integrating data into a pre-existing information system." (Biscobing, 2019)















Reference List

         Biscobing, J. (2019) What is entity relationship diagram (ERD)?: Definition from TechTarget, Data Management. TechTarget. Available at: https://www.techtarget.com/searchdatamanagement/definition/entity-relationship-diagram-ERD (Accessed: March 12, 2023).

         Freepik (2020) Free vector: Flow diagram infographic template, Freepik. Available at: https://www.freepik.com/free-vector/flow-diagram-infographic-template_8968645.htm#query=entity%20relationship%20diagram&position=10&from_view=search&track=ais (Accessed: March 12, 2023).

         Javapoint (no date) Er (entity relationship) diagram model in DBMS examples - javatpoint, www.javatpoint.com. Available at: https://www.javatpoint.com/dbms-er-model-concept (Accessed: March 12, 2023).

         Visual-paradigm (2022) What is entity relationship diagram (ERD)? Available at: https://www.visual-paradigm.com/guide/data-modeling/what-is-entity-relationship-diagram/ (Accessed: March 12, 2023).

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