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DBMS BCA Unit-2 ER Model - Introduction Components of an E-R Model Entity Entity Identifier: Key Attributes Strong and Weak Entity Sets Attributes and Domain Types of Attributes Relationships E-R DIAGRAM ERD for STUDENT Entity ERD for CAR Entity Entity Types for a COMPANY Database Relationship Types of COMPANY Database THE RELATIONAL MODEL Structure of Relational Databases Super Keys and Candidate Keys Relational Constraints Database Operations and Constraint Violations


THE RELATIONAL MODEL

A model in database system basically defines the structure or organization of data and a set of operations on that data.

In Relational Model database is represented as a collection of “Relations”, where each relation is represented by a two dimensional table. Database Management System

Advantages of relational model:
  • Ease of use - The simple tabular representation of database helps the user to define and query the database conveniently.
  • Flexibility - Since the database is a collection of tables, new data can be added and deleted easily. Also, manipulation of data from various tables can be done easily using various basic operations.
  • Accuracy - In relational databases the relational algebraic operations are used to manipulate database. These are mathematical operations and ensure accuracy as compared to other models.