Module - Case Entity-Relationship Model and Database Design
Apply what you learned in the following exercise:
Tables in an Electronics Store
A fairly large local electronics store contracts with you to develop a database system for them. Your first task is to design a table for the store's employees.
Even many of the most experienced designers "sketch" a design on paper before they start creating the database in electronic form.
Please "sketch" an employee table (basically what data items or columns should be included in the table) using the template below as a model.
The CEO of the store tells you that the following information must come from the table.
1. List/display of all employees showing social security number, first and last name, address, city, state and zip code, birth date, full-time or part-time status, salary (hourly rate) and date of hire.
2. The total number of employees.
3. List/display of all employees making more than a certain hourly rate, say $20 per hour.
4. List/display of all employees hired within a time period, say last year.
"Template" for Employee's Table
EMPLOYEE TABLE
Social Security Number
The data items that belong in a table are a function of the information that has to come out of the table. Therefore, the determining factor is the information requirements that have been given to you.
This is your assignment:
Part I
1. Enter the data items in the column headings in row one that you believe should be in this table. In doing this, you are actually designing the table.
2. Paste your table into a document.
3. Go to Part II below and complete the assignments there.
HINTS for Part I:
You need not be concerned with the rows (except for row one, of course).
The first column of the table is the Primary Key (social security number). This has been filled in to give you a start.
Match what's in your table to the information requirements to make certain all data has been included.
Totals that are derived from the table through computation do not have to be carried in the table.
Part II (Required)
Your work is so good that the electronics store contracts with you to do additional work for them. Your next task is to design two tables that relate to one another. These tables are: the Customer table and the Sales Order table.
The Customer table contains the basic data on each customer, and the primary key is the customer number. There is one row for each customer.
The Sales Order table contains the data for each sale. The primary key consists of two pieces of data: sales order number and customer number. There can be one or more sales orders for a customer, but only one customer on a sales order.
Use the templates below to design the two tables.
"Templates" for Table Design
Customer Table
Sales Order Table
Case Assignment
Entity-Relationship Modeling
1. Fill in the column headings in row one of each table with the data items you believe belong in the table.
2. Cut and paste your tables into the same document from Part I.
3. Suppose the Sales Order table also contains information for an employee who makes a sale. Draw an ERD of your complete design for the electronic store. If you have an ERD drawing tool such as Visio, you could draw the diagram using the tool and copy it into your document. You could also draw it on paper, scan it, and insert it into your document. If you can't do either of the above, you could write down the table schemata and describe the relationships among them.
4. Submit the document. Make certain the table title, course number, and module and Case ID are on the work you submit.
5. Describe the major points you learned in the readings especially on entity-relationship modeling and what lessons you have learned in this exercise. (at least half a page).
HINT: Search the Internet to find help either in the form of examples or similar problems or tutorials.
Assignment Expectations
• Design tables based on domain requirements.
• Represent database design using ERD.
• Communicate effectively with your audience.