Entity

What is an Entity?

An entity represents a distinct object or concept within a system or database. Here’s a breakdown:

• Actual Item: In databases, an entity represents a real-world object or concept, like a “Customer” or “Product.” Each entity has specific attributes (such as “Name” or “ID”) that describe it.
• E-R Diagram Example: In an E-R diagram, entities are depicted as boxes. These boxes contain information about the entity and are connected to other entities through relationships. For instance, a box labeled “Employee” might be connected to a box labeled “Department” to show that employees belong to departments.

Visualizing an Entity

1. Database Example: In a database, entities are often represented as tables or records. For example, a table named “Employees” might contain data about various employees, with each record representing an individual employee.
2. E-R Diagram Example: In E-R diagrams, entities are shown as rectangles or boxes. These boxes are used to illustrate different data elements and how they relate to each other within the system.

Important Notes

• The term “entity” is used in various contexts, including databases and programming (e.g., Java’s EJB). Its exact meaning may vary depending on the context.
• Generally, when you encounter the term “entity,” think of it as representing an actual item or object, especially in the context of E-R diagrams where it denotes specific components or elements.

Summary

When you see the term “entity,” it typically means “an actual item or object,” and in E-R diagrams, it refers to the boxes that represent different objects or concepts in a system.