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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


Relationships

A relationship can be defined as:
  • A connection or set of association, or
  • A rule for communication among entities.
eg:- In the college database, the association between Student and Programmes entity "Student opts Programmes" is a relationship.