What is an ERD. Define the ERD related terms, including entities, attributes, cardinalities and relationships

 

ERD (no date)

What is an ERD?

An entity relationship diagram (ERD), also known as an entity relationship model, is a graphical representation that depicts relationships among people, objects, places, concepts or events within an information technology (IT) system. An ERD uses data modelling techniques that can help define business processes and serve as the foundation for a relational database.

ERD TERMS:

Entities: Which are objects or concepts that can have data stored about them. Entities refer to tables used in databases.

Attributes: Which are properties or characteristics of entities. An ERD attribute can be denoted as a primary key, which identifies a unique attribute, or a foreign key, which can be assigned to multiple attributes.

Relationship: The relationships between and among those entities.

Cardinality ratio: How many instances of one entity is related with another, and there is three cardinalities:

1. One-to-one relationship (1:1). For example, if each customer in a database is associated with one mailing address.

2. One-to-many relationship (1:M). For example, a single customer might place an order for multiple products. The customer is associated with multiple entities, but all those entities have a single connection back to the same customer.

3. Many-to-many relationship (M:N). For example, at a company where all call center agents work with multiple customers, each agent is associated with multiple customers, and multiple customers might also be associated with multiple agents.(Biscobing, 2019)

Reference:

Entity relationship diagram (ERD) (no date) Entity Relationship Diagram (ERD) - What is an ER Diagram? Available at: https://www.smartdraw.com/entity-relationship-diagram/ (Accessed: March 14, 2023).

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 14, 2023).