Revision
Practical task
Formative Test
Entity-Relationship Diagrams (ERD) PART 2
Learning objective
ERD (Entity Relationship Diagram)
An entity-relationship diagram (ERD) is a type of data modeling that shows a graphical representation of objects or concepts within an information system or organization and their relationship to one another.
The elements of an ERD are:
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What is an ER diagram?
Uses of entity relationship diagrams
ERD symbols and notations
Limitations of ER diagrams and models
How to draw a basic ER diagram
ERD Exercises
A manufacturing company produces products. The following product information is stored: product name, product ID and quantity on hand. These products are made up of many components. Each component can be supplied by one or more suppliers. The following component information is kept: component ID, name, description, suppliers who supply them, and products in which they are used. U for this exercise.
Create an ERD to show how you would track this information.
Show entity names, primary keys, attributes for each entity, relationships between the entities
ERD Exercises
ERD Answer
Component(CompID, CompName, Description) PK=CompID
Product(ProdID, ProdName, QtyOnHand) PK=ProdID
Supplier(SuppID, SuppName) PK = SuppID
CompSupp(CompID, SuppID) PK = CompID, SuppID
Build(CompID, ProdID, QtyOfComp) PK= CompID, ProdID
ERD Exercises
ERD Exercises
Exercise 1 : Each of the MegaCo Corporation’s divisions is composed of many departments. Each of the departments has many employees assigned to it, but each employee works for only one department. Each department is managed by one employee, and each of these managers can manage only one department at a time.
Exercise 2 : During some period of time, a customer can rent many videotapes from the BigVid store. Each of the BigVid’s videotapes can be rented to many customers during that period of time.
ERD Exercises
Exercise 3 : Pick and Shovel Construction Company is a multi-state building contractor specializing in medium-priced town homes. Assume that Pick and Shovel’s main entities are its customers, employees, projects and equipment. A customer can hire the company for more than one project, and employees sometimes work on more than one project at a time. Equipment, however, is assigned to only one project at a time. Draw an ERD showing those entities.
Project Work
Create ER Diagram for the new system.Show entity names, primary keys, attributes for each entity, relationships between the entities