Examples of E-R model

The ER (Entity-Relationship) model represents real-life scenarios as entities. The properties of these entities are their attributes, and their connections are shown as relationships. ER models help visualize how data is structured in a database system.

Hospital ER Model

This ER model has three entities − Patient, Doctor, and Tests ?

Entities and their attributes −

• Patient − ID (primary key), Name, Age, Visit_date
• Tests − Name (primary key), Date, Result
• Doctor − ID (primary key), Name, Specialization

Patients consult Doctors, Patients take Tests, and Doctors conduct Tests.

Company ER Model

This ER model has three entities − Employee, Department, and Project ?

Entities and their attributes −

• Employee − ENO (primary key), Name, Salary
• Department − DNO (primary key), Name, Locations
• Project − PNO (primary key), Name

Employees work for Departments, Departments control Projects, and Employees work on Projects.

Conclusion

These ER model examples demonstrate how complex real-world scenarios can be simplified into entities (rectangles), attributes (properties), and relationships (diamonds). The Hospital model shows patient-doctor-test interactions, while the Company model captures employee-department-project associations.