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

Entity Relationship Diagram (ERD)

An entity relationship diagram (ERD), also known as an entity relationship model, is a graphical representation that depicts relationships between objects, places, concepts, or events within an information technology (IT) system. An ERD uses data modelling approaches to build business processes and lay the foundation for a relational database (Biscobing, 2019).

Entity relationship diagrams assist establish the requirements for an organization's information systems and provide a visual starting point for database architecture. When a relational database has been implemented, an ERD can still be utilised as a reference in the event that additional debugging or re-engineering of business processes is necessary.

An ERD can assist in the organisation of data that can be represented by a relational structure, but it cannot effectively represent semi-structured or unstructured data. Also, it is unlikely to be helpful on its own in integrating data into an information system that already exists(Biscobing, 2019).

(visual-paradigm.com,2023)

Entities, attributes, and relationships make up the basic three components of ER diagrams, often known as ERDs.

Entities -Which are often shown as rectangles, might be objects, people, concepts, or events that hold data.

Attributes-The properties of an entity are referenced by the attributes, which are shown as a circle or oval. An object can have one or more attributes, which are divided into simple, composite, and derived categories.

Relationships-Show the relationship between two or more entities. On the lines separating the objects, they are shown as labels (Biscobing, 2019).

A cardinality notation can then be used to describe the properties of the link between the objects. When determining whether an entity is essential or optional, cardinalities might be used (for example, a sales representative may have many or no customers) (for example, there must be at least one product listed in an order.)

The three fundamental principles are:

1. A one-to-one relationship (1:1)- For instance, imagine that each customer in a database is linked to a single postal address.
2. A one-to-many relationship (1:M)-An individual consumer might order many things, for instance. Although the customer is connected to numerous entities, each of those entities only has one path leading back to the same customer.
3. A many-to-many relationship (M:N)- For instance, at a company where all call centre agents deal with many clients, each agent is linked to a number of those customers, and those customers may be linked to a number of different agents(Biscobing, 2019).

Reference

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).

Free entity relationship diagram tool. Available at: https://www.visual-paradigm.com/solution/free-erd-tool/ (Accessed: March 12, 2023).