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

Entity Relationship Diagrams

(lucidchart.com, 2023)

Entity Relationship Diagrams, or ERDs, are diagrams that show the connections between entities in a database. To assist developers and stakeholders in understanding the structure and relationships of the data in a system, it is frequently used in software engineering and database architecture. Entities are things or ideas with qualities and independent existence. An entity that might have attributes like "name," "address," and "email" is referred to as a "customer," for instance (lucidchart.com, 2023)

An entity's attributes are its traits or possessions. For instance, the name of a client would be stored in the "name" attribute of the customer entity. Cardinalities show how many instances of one entity can be connected to another and describe the links between entities. The "one-to-one," "one-to-many," and "many-to-many" cardinalities are the most prevalent (visual-paradig.com, 2023).

One-to-one:

When one instance of one entity is linked to one instance of another, this is known as a one-to-one relationship. A "person" entity and a "address" entity, for instance, can have a one-to-one relationship in which each person has a single address (Glen, 2021).

One-to-many:

When one instance of one entity is linked to numerous instances of another entity, this is known as a one-to-many relationship. For instance, a "department" entity and a "employee" entity can have a one-to-many relationship in which each department includes numerous employees (gatevidyalaya.com, 2020).

Many-to-many:

When several instances of one entity are linked to multiple instances of a different entity, this is known as a many-to-many relationship. For instance, a "student" entity and a "course" entity might have a many-to-many relationship in which each student can take a variety of courses and each course can have a variety of students (visual-paradig.com, 2023). 

In conclusion, an ERD is a tool for displaying the connections between entities in a database. Cardinalities explain the relationships between entities, while attributes are the traits or properties of an entity. Entities are things or concepts having attributes.

Reference:

lucidchart.com, (2023). What is an Entity Relationship Diagram (ERD)? [Online] Available from: https://www.lucidchart.com/pages/er-diagrams (Accessed 5 March 2023).

gatevidyalaya.com, (2020). Cardinality inER Diagram | DBMS : Types of Cardinality Ratios- [Online] Available from: https://www.gatevidyalay.com/cardinality-in-er-diagram/ (Accessed 5 March 2023).

Glen, Stephanie. (2021). E-R Diagram Cardinality and Participation [Online] Available from: https://www.datasciencecentral.com/e-r-diagram-cardinality/ (Accessed 5 March 2023).

visual-paradig.com, (2023). What is an Entity Relationship Diagram (ERD)? [Online] Available from: https://www.visual-paradigm.com/guide/data-modeling/what-is-entity-relationship-diagram/ (Accessed 5 March 2023).