JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III Year DATABASE MANAGEMENT SYSTEMS Previous Question Paper (March - 2024 - R16)

A data model is a conceptual framework or collection of tools used to describe the structure of a database, including the data itself, the relationships between data elements, data semantics, and consistency constraints. It provides a way to represent the real-world information requirements in a structured format that can be implemented in a database management system.

Key components of a data model include:

• Data Entities: The objects or concepts about which data is stored.
• Attributes: The properties or characteristics of those entities.
• Relationships: The associations or links between different entities.
• Constraints: The rules that govern the integrity and validity of the data.

Data models act as a bridge between the real-world requirements and the physical storage of data, allowing designers to communicate the database structure effectively. Common types include the Relational Model, Entity-Relationship (ER) Model, Object-Oriented Model, and Hierarchical Model.

A View in a database is a virtual table based on the result-set of an SQL statement. It does not store data itself but provides a dynamic window into the underlying base tables. To create a view, the CREATE VIEW statement is used.

The general syntax for creating a view is as follows:

The process involves the following steps:

• Naming the View: Provide a unique name for the view that follows standard database naming conventions.
• Defining the Query: Specify the SELECT statement that retrieves the desired data from one or more tables. This query defines the structure and content of the view.
• Execution: Once the CREATE VIEW command is executed, the database stores the definition of the view in the data dictionary.

Example:

CREATE VIEW Employee_Details AS 
SELECT Name, Department 
FROM Employees 
WHERE Salary > 50000;

After creation, the view can be queried just like a physical table using the SELECT command: SELECT * FROM Employee_Details;.