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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


Relationship Types of COMPANY Database

Six Relationship Types are identified:
  • WORKS_FOR (between EMPLOYEE, DEPARTMENT)
  • MANAGES (also between EMPLOYEE, DEPARTMENT)
  • CONTROLS (between DEPARTMENT, PROJECT)
  • WORKS_ON (between EMPLOYEE, PROJECT)
  • SUPERVISION (between EMPLOYEE (as subordinate), EMPLOYEE (as supervisor)) DEPENDENTS_OF (between EMPLOYEE, DEPENDENT)
Database Management System