What is an ERD?

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What is an ERD?

An ER diagram or entity-relationship diagram is a visual representation of entities and relationships within a database (Chen, 1976). It represents the entities in a database as rectangles and relationships between the entities as lines connecting the rectangles.

Entities?

Entities refer to objects or concepts within a domain that are identifiable and distinct (Korth et al., 2009). In a database, entities are represented as tables that store data related to them. For example, in a database for a university, entities can be students, faculty, courses, departments, and programs.

Cardinalities?

Cardinalities are the numerical values that define the relationship between entities. They represent the number of instances in one entity that can be associated with the number of instances in another entity (Hevner et al., 2004). The cardinalities are expressed using symbols such as “1”, “M” and “N”. For example, in a database for a university, the cardinality between a student and a course can be represented as one-to-many (1:M) since one student can enroll in many courses.

Relationships?

Relationships refer to interactions or associations between entities (Korth et al., 2009). It describes how two or more entities are connected and related to each other. In a database, relationships are represented as a line connecting entities. For example, in a university database, a student entity can have a relationship with a course entity, indicating that a student has enrolled in a particular course.

    In summary, ER diagrams provide a visual representation of entities, their relationships, and the cardinalities between them. It is a useful tool for developers to design and model databases and understand the relationships between various entities in a database.

Reference List:

Chen, P. P. (1976). The Entity-Relationship Model: Toward a Unified View of Data. ACM Transactions on Database Systems (TODS), 1(1), 9-36. (Accessed: 3rd September 2023).

Hevner, A. R., March, S. T., Park, J., & Ram, S. (2004). Design Science in Information Systems Research. MIS Quarterly, 28(1), 75-105. (Accessed: 3rd September 2023).

Korth, H. F., Silberschatz, A., & Sudarshan, S. (2009). Database System Concepts. McGraw-Hill Higher Education. (Accessed: 3rd September 2023).