JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD MCA 2019 DATABASE MANAGEMENT SYSTEMS Previous Question Paper (April/May - 2019 - R13)

Data models are conceptual tools used to describe data, data relationships, and constraints. The primary types are:

• Relational Model: Represents data in the form of tables consisting of rows and columns.
• Entity-Relationship Model: Uses entities, attributes, and relationships to represent real-world objects.
• Object-Oriented Model: Organizes data as objects containing both data and methods.
• Hierarchical/Network Models: Represent data using tree-like or graph-like structures respectively.

Set operations are relational algebra operations used to combine the results of two compatible relations into a single result set. The fundamental set operations include:

• Union (∪): Combines all tuples from two relations, removing duplicates.
• Intersection (∩): Returns only the tuples that are present in both relations.
• Set Difference (−): Returns tuples that exist in the first relation but not in the second.
• Cartesian Product (×): Combines every tuple of the first relation with every tuple of the second.