ER Diagrams
Submit a single MS Word document and the end of this tutorial.
Use an online drawing tool (like draw.io or Lucidchart) to create the ER Diagrams. Be sure to include your name within each drawing inside a text box. Then place the drawing in your MS Word document, which you could do using the screenshot tool.
1. True or False: An Entitiy in an initial ER Diagram is always a table in a the final database
2. Order these entity relationships from least to most favourable - one-to-one, many-to-many, one-to- many
3. Why do we try to avoid many-to-many relationships in our databases?
4. When we draw crows-feet on the lines between entities, are we marking cardinality or existsence?
5. When we draw circles and vertical lines on the lines between entities, are we marking cardinality or existsence?
6. Create ER Diagrams for the following scenarios:
a. A database stores information about products and warehouses. A product is identified by a product number, and has a description and quantity available. Warehouses are identified by a warehouse number and have a name and address. Products are stored in warehouses. Each warehouse may store many product types, but a particular product type can only be stored in one warehouse.
b. A department is identified by a department number and has a title and budget. Department Projects are identified by a project number and have a start date and end date. Each project can only take place in one department, although each department can have several projects running at the same time.
c. Your school database contains these 3 tables - courses, subjects, and lecturers. A course consists of many subjects, and each subject can only be associated with one course. Each subject is co-ordinated by a single lecturer and each lecturer can co-ordinate more than one subject. Subjects and courses are identified by subject and course codes, and have a name. Lecturers are identified by an ID and have a name, room number and telephone contact number.
i. Draw the ER diagram
ii. How would you change your database if each subject could be in more than one coures?
iii. What if one lecturer could only co-ordinate one subject?
d. What would the database look like if your description for question 1 changed, so that a product can be stored in more than one warehouse?