Entity:
An entity is any object or thing in the real world that can be distinctly identified and represented in a database.
- An entity can be a person, object, event, or concept that must have an attribute and a unique key.
Example: In a university database, a “Student” or “Course” would be an entity.
Entity Types:
An entity type defines a collection of similar entities that share the same set of attributes.
- It acts as a blueprint for describing entities of a particular kind in the database.
Example: In a university database, the entity type “Student” may have attributes such as “Student ID,” “Name,” “Date of Birth,” and “Major.”
Entity Set:
An entity set is the collection of all entities of a particular entity type in a database at a given point in time.
- It represents the complete set of instances of that entity type.
Example: The entity set “Students” would contain all the students (entities) currently recorded in the university database.