1. CIS336 Week 1 iLab1
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LABOVERVIEW
Scenario/Summary
This lab will introduce you to the processes involved in defining one of the key
components of a data model; the relationship diagram (RD). In this lab, you will
draw a relationship diagram for two of the steps shown. Keep in mind when you
are trying to decide which side of the relationship should be the "one" side and
which should be the "many" that you must first decide which side has the primary
key, or unique identifier. Once you have decided the primary key of the
relationship, you have identified the "one" side of the relationship. Note that for an
RD, the foreign key "many" side of the relationship points to the primary key "one"
side. The "one" side should have the arrowhead point of the connecting line. This
is different than an entity/relationship diagram (ERD) that we will draw next week,
where the "many" side has crow's feet.
This will familiarize you with how to set up MS Visio to draw database diagrams.
Steps 1 - 3 below use the Customer, Order, and Employee tables of a simplified
Order Entry database. The Customer table records clients who have placed
orders. The Order table contains the basic facts about customer orders. The
Employee table contains facts about employees who take orders. The primary
keys of the tables are CustNo for Customer, EmpNo for Employee, and OrdNo for
Order.
The following are the TABLE definitions for the first three tables showing the
PRIMARY KEY constraints.
TABLE Customer has the following attributes
CustNo
NUMBER(5)
CustFirstName
VARCHAR2(20)
CustLastName
VARCHAR2(30)
3. DATE
CustNo
NUMBER(5)
EmpNo
NUMBER(5)
OrdNo is the
PRIMARY KEY
Your task for this lab is to create the required relationship diagram for steps 1 and
2 using Microsoft Visio. Step 3 will require you to analyze the scenario given and
present your own resolution to the question. Step 4 is an individual assignment
that will introduce you to the group project and the process of identifying entities
and attributes. When finished with the lab, you should have a complete diagram
using all 5 entities, a written explanation for #3, and two lists (entities and
attributes) for Step 4.
Deliverables
The deliverable for this lab is a single MS Word document named
"Lab1_solution_yourname" with the diagram for problems 1 and 2, the written
answer for the question in Step 3, and the lists of entities and attributes for the
Initial Project Exercise (Step 4). You should copy and paste the diagram from MS
Visio into a Word document and use this document for Steps 3 and 4.
LABSTEPS
STEP 1: Drawing your first ER diagram Title
Identify the foreign key columns in the table structures above and draw a
relationship diagram depicting the relationships between the tables. In the Order
table , the CustNo column references the Customer table and the EmpNo column
references the Employee table. For each relationship, identify the table on the "1"
side of the relationship and the table on the "Many" side.
STEP 2: Extending the ER diagram
4. Extend your relationship diagram from problem 1 by adding two tables (OrdLine
and Product). Table definitions for the table structures and primary keys
constraints are shown below. You will need to identify the FOREIGN KEY(s) to
complete this problem. When finished you should have a total of 5 tables
represented in your diagram for this problem. To copy and paste the diagram into
Word, select Edit from the menu and then Copy Diagram. Open a Word
document and use CTRL-V to paste the diagram.
TABLE Product has the following attributes
ProdNo
CHAR(8)
ProdName
VARCHAR2(20)
ProdNo is the
PRIMARY KEY
TABLE OrdLine has the following attributes
OrdNo
CHAR(8)
ProdNo
CHAR(8)
Qty
NUMBER(5)
The combination of OrdNo and Prodno is the
PRIMARY KEY
STEP 3: Should a NULL be allowed?
From examination of the sample data and your current understanding of
businesses in which orders could be placed either in person, over the phone, or
5. over the Internet, determine if it would be permissible for null values to be allowed
for the foreign key EmpNo in the Order table. This column would reference back
to the EmpNo column in the employee table. Why or why not?
OrdNo
OrdDate
CustNo
EmpNo
O1656777
02/11/2000
C8543321
O7959898
02/19/2000
C8543321
E8544399
STEP 4: Initial Project Exercise
Although the overall project itself will be done as a group, this first exercise is
designed as an individual effort and is intended to; (1) get you to read the project
specifications, and; (2) introduce you to the first step in designing a database
from scratch. This little exercise will have you see how many entities and
attributes you can find in the project specifications. In week three, you will work
with your assigned project team and compare notes on what you have found.
This is not rocket science here so remember, you are looking for people, places,
things, and events (entities) and the attributes that describe them.
