In a database management system (DBMS), an entity is a piece of data that is stored in the database. An entity is an object or thing that exists in the real world, such as a customer, car, or pen. Entities are distinguishable, meaning each entity in a pair of entities has a property that makes one entity different from the other entity. An entity can be represented in a database using some attributes and is associated with other entities using some relationship.
Here are some key terms related to entities in DBMS:
- Entity type: It refers to the category that a particular entity belongs to. For example, a table named "student" in a university database is an entity type.
- Entity set: An entity set is a collection or set of all entities of a particular entity type at any point in time. For example, all the students in a university database would be an entity set.
- Weak entity: A weak entity in DBMS does not have a key attribute and depends on some other strong entity to be identified uniquely. For example, if "installment" is an entity, then it can exist only if a "loan" exists as an entity.
Overall, entities are an essential part of DBMS as they represent real-world objects and are used to manage data in a database.
