In a Relational Database Management System (RDBMS), data is organized and stored in a tabular form known as tables. The data in RDBMS is structured and follows a predefined schema, consisting of tables, columns, and relationships. There are two fundamental views of data in an RDBMS:

1. Physical View: The physical view refers to how the data is physically stored on the underlying storage media, such as hard drives or solid-state drives. It deals with aspects such as disk space allocation, file organization, indexing methods, and data storage formats. The physical view is primarily concerned with optimizing storage efficiency and performance.

2. Logical View: The logical view represents the way users perceive and interact with the data. It focuses on the conceptual organization of the data and the relationships between various entities. The logical view is concerned with data integrity, consistency, and providing a user-friendly and meaningful representation of the data.

Within the logical view, there are two important concepts:

- Entity-Relationship (ER) Model:

The Entity-Relationship (ER) model is a conceptual modeling technique used in database design to represent the entities, relationships, and attributes of a system. It helps to visualize and understand the structure and behavior of a database system.

Let's consider an example to illustrate the Entity-Relationship (ER) model:

Suppose we are designing a database for a university. The main entities in this scenario could be "Student," "Course," and "Department." Each entity has its attributes, and there are relationships between them.

Here's a simplified representation of the ER model for this example:

1. Entity: Student

- Attributes: StudentID, FirstName, LastName, DateOfBirth, Email
- Relationships: Enrolls in (with Course entity), Belongs to (with Department entity)

2. Entity: Course

- Attributes: CourseID, CourseName, Credits
- Relationships: Offered by (with Department entity), Taken by (with Student entity)

3. Entity: Department

- Attributes: DepartmentID, DepartmentName, Location
- Relationships: Offers (with Course entity), Has (with Student entity)

In this ER model, we have identified three entities: Student, Course, and Department. Each entity has its attributes that describe the specific information related to that entity. For example, the Student entity has attributes like StudentID, FirstName, LastName, DateOfBirth, and Email.

Additionally, there are relationships established between the entities. For instance, a student can "Enroll in" multiple courses, creating a relationship between the Student and Course entities. Similarly, a course can be "Offered by" a particular department, creating a relationship between the Course and Department entities.

The ER model allows us to visualize these relationships and understand the dependencies between entities. It provides a high-level representation of the database structure and assists in the design and implementation of the actual database schema.

Note that the ER model is a conceptual model and doesn't include all the details of the database schema, such as primary keys, foreign keys, and specific constraints. It serves as a foundation for creating an actual database design and can be further refined into a logical or physical data model.

By using the ER model, database designers can capture the important entities, attributes, and relationships of a system, helping to ensure that the database structure accurately represents the requirements and operations of the system being modeled.

- Relational Model: The relational model is based on the concept of tables, which are also known as relations. Each table consists of rows (tuples) and columns (attributes). The relational model establishes relationships between tables using primary keys, foreign keys, and other constraints. It provides a mathematical foundation for organizing and manipulating data in a tabular format.

The RDBMS manages the mapping between the physical view and the logical view, ensuring that data is stored and retrieved efficiently while maintaining the integrity and consistency of the logical structure. Users interact with the RDBMS through a query language, such as SQL (Structured Query Language), which allows them to perform operations like querying, inserting, updating, and deleting data.

Overall, the physical view deals with the storage and performance aspects, while the logical view focuses on the conceptual organization and meaningful representation of the data in an RDBMS.

About the Author

Silan Software is one of the India's leading provider of offline & online training for Java, Python, AI (Machine Learning, Deep Learning), Data Science, Software Development & many more emerging Technologies.

We provide Academic Training || Industrial Training || Corporate Training || Internship || Java || Python || AI using Python || Data Science etc