Database Systems: Design, Implementation, & Management
Database Systems: Design, Implementation, & Management
12th Edition
ISBN: 9781305627482
Author: Carlos Coronel, Steven Morris
Publisher: Cengage Learning
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Chapter 2, Problem 6RQ
Program Plan Intro

Entity Relationship Diagram (ERD):

Entity relationship diagram is a basically a picture or snapshot about the business system. It means that the information stored and created is represented by this diagram.

  • Entities may represent the physical object, event, or concept.
  • An attribute is a property of an entity.
  • Relationship denotes the link between the entities.
    • If an independent child entity is present in a relationship then it is called a non-identifying relationship.
    • If a dependent child entity is present in a relationship then it is called a identifying relationship.

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Use ER Assistant to draw your diagram.   Draw a self-referencing entity type for the Employee entity type for which an employee is supervised by a maximum of one other employee and doesn’t have to be supervised by any employee at all. Conversely, an employee can supervise zero or many other employees.  The attributes of the Employee entity are as follows:  EmpNo (primary key), EmpName, EmpAddress.
Draw an entity-relationship diagram, including minimum and maximum cardinality, for the following: The system stores information about two things: cars and owners. A car has attributes for make, model, and year. The owner has attributes for name and address. Assume that a car must be owned by one owner and an owner can own many cars, but an owner might not own any cars (perhaps she just sold them all, but you still want a record of her in the system).
The distinction between a weak and a strong entity set is best explained here.
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