What is an Entity And Its Types?
Anything about which an organization (or we) wants to collect information is called Entity.
Entities are used to represent real-world objects within the database, and they serve as the foundation for organizing and structuring data in a database management system (DBMS).
Entities are typically used in the Entity-Relationship Model (ER Model). A popular database modeling technique that is used to design and define the structure of a database.
Example:
In a database, an entity often corresponds to a table. It represents a specific category or type of information, such as “Doctor,” “Patient,” or “Nurse.”
Each entity has attributes (columns) that describe the properties and characteristics of instances (rows) within that category.
Entities are used to organize and structure data within a database. The database makes it easier to store, retrieve, and manage information related to real-world objects.
What is Entity Set?
An entity set is a collection of similar entities in a database.
An entity set is a logical grouping of these entities based on shared characteristics. It gathers together entities that are alike and have the same type of information.
For example, if you have a database for a library, the “Books” entity set would contain all the individual book entities, making it easy to manage and access information about books collectively.
What is an Entity Instance?
For example, if you have a database for a library, the “Books” entity set would contain all the individual book entities, making it easy to manage and access information about books collectively.
Entity and its Types:
There are 5 basic types of entity which are as follows:
- Strong Entity:
- Definition: A strong entity is a type of entity that has its distinct existence and can be uniquely identified independently.
- Example: “Car” is a strong entity because you can describe a car on its own without needing additional information.
- Weak Entity:
- Definition: A weak entity is an entity that cannot be uniquely identified by its attributes alone and depends on a related strong entity for identification.
- Example: “License Plate Number” is a weak entity because it doesn’t uniquely identify a vehicle by itself; you need the “Vehicle” (strong entity) it’s attached to.
- Associative Entity:
- Definition: An associative entity is used to connect and describe the relationship between two or more strong entities in a database.
- Example: In a library database, “Borrowing” can be an associative entity that connects “User” and “Book” entities to show who borrowed which book and when.
- Abstract Entity:
- Definition: An abstract entity represents something that is conceptual or not directly tangible, like ideas, concepts, or feelings.
- Example: “Friendship” is an abstract entity because it represents the concept of a close and positive relationship between people.
- Derived Entity:
- Definition: A derived entity is a type of entity that is calculated or derived from other attributes or entities in a database.
- Example: “Age” can be a derived entity in a “Person” entity, calculated by subtracting the “Birthdate” from the current date.
Related: Databases and Types of Databases with Real-Life Examples
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