1. Mia’s Sandwich Shop: An introduction to database design

2. Your mission To investigate some of the real-life issues that face database design

3. Investigate a poorly designed system Objectives Identify some key issues in database design By the end of the session you should be able to: Identify the exact nature of the data handling problems

4. ….through a case study called Mia’s Sandwich Shop

5. Stage 1 Meet Mia and begin to understand her business.

6. Stage 2 Identify the roles of the various staff who work for Mia.

7. Stage 3 Run a simulation of how the business works.

8. Stage 4 What have we learned?

9. What are the problems? Redundant data Repeated data Human error Inflexibility

10. Redundant and repeated data Each time a customer orders a product it is necessary to record their address. Each row contains a code for the product as well as the product name. For every order the information has to be written out again on the delivery note.

11. Potential for human error Order clerk has to look at the menu sheet to find the product code and price. If a customer orders more than one sandwich the total cost has to be manually calculated.

12. Inflexibility 1 Difficult to make changes: Once the order is placed To the customer details Difficult to determine the total cost of order. Difficult to see how many of a particular product had been ordered that day.

13. Inflexibility 2 The system: Only holds information on customers when they have placed an order. Only hold information on products once they have been ordered. If an order is removed, valuable information is lost.

14. Summary Today we have: Investigated the roles of the workers in the business Looked at problems that can arise from poorly designed systems.