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CHAPTER 5
DATABASES
Entity-Relationship Modeling
(ER-M)
Jason C. H. Chen, Ph.D.
Professor of MIS
School of Business Administration
Gonzaga University
Spokane, WA 99258
chen@jepson.gonzaga.edu
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1. Data Modeling (Student-Advisor)
• Each semester, each student must be assigned an adviser
who counsels students about degree requirements, and
helps students register for classes. Each student must
register for chasses with the help of an adviser, but if the
students’ assigned adviser is not available, the student may
register with any adviser. We must keep track of students,
the assigned adviser for each, and the name of the adviser
with whom the student registered for the current term
(therefore, there is a relationship between “Student” and
“Course”). Represent this situation of students, advisers and
course with an E-R diagram. Also, draw a data model for this
situation using the tool you have been told to use in your
course.
– Entity and attributes
– Relationship and cardinality
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1a)
Advisor
Student
Course
Ad_ID
S_ID
C_ID
Ad_Name
Ad_Department
S_Name
S_Major
C_Title
C_Credits
1b) break down M:N into two 1:M
Advisor
Student
Course
Ad_ID
S_ID
C_ID
Ad_Name
Ad_Department
S_Name
S_Major
C_Title
C_Credits
Student_Advisor
Enrollment
Ad_ID
S_ID
C_ID
S_ID
Semester
Year
Semester
Year
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2. Data Modeling (Project – Employee)
• A company has a number of employees. The attributes
of EMPLOYEE include Employee_ID (identifier), Name
Address and Birthdate. The company also has many
projects with Project_Name and Start_Date, Expected
finish date, and Budget. Each employee may be
assigned to one or more projects, or may not be
assigned to a project. A project must have at least one
employee assigned and may have any number of
employees assigned. An employee’s billing rate for a
project may vary by project and the company wishes to
record the applicable billing rate (Billing_Rate) for each
employee when assigned to a particular project. A client
normally asks the company working more than one
project for them. The attributes of CLIENT includes
Client_ID, Name, Address, Contact, Title and Phone.
– Entity and attributes
– Relationship and cardinality
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2 a)
step-1
2 b)
step -2
break
down
M:N
into
two
1:M
Client
Project
Employee
Client_ID
Proj_ID
Emp_ID
Name
Address
Contact
Title
Phone
Proj_Name
Start_Date
Exp_Fin_Date
Budget
Name
Address
DOB
Client
Project
Client_ID
Proj_ID
Name
Address
Contact
Title
Phone
Proj_Name
Start_Date
Exp_Fin_Date
Budget
Billing (or
Project_Employee)
Emp_ID
Proj_ID
Billing Rate
Employee
Emp_ID
Name
Address
DOB
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3. Data Modeling (Physician)
• A hospital has a large number of registered physicians,
Attributes of Physician include Physician_ID (the identifier)
and Specialty. Patients are admitted to the hospital by
physicians. Attributes of Patient include Patient_ID (the
identifier) and Patient_Name. Any patient who is admitted
must have exactly one admitting physician. A physician may
optionally admit any number of patients. Once admitted, a
given patient must be treated by at least by a physician. A
particular physician may treat any number of patients, or may
not treat any patients. Whenever a patient is treated by a
physician, the hospital wishes to record the details of the
treatment (Treatment_Detail). Components of
Treatment_Detail include Date, Time, and Results. Did you
draw more than on e relationship between physician and
patient? Why or why not?
– Entity and attributes
– Relationship and cardinality
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3 a)
Physician
Patient
Physician_ID
Patient_ID
Specialty
Admits
Pat_Name
Treats
3 b) break down M:N into two 1:M
Physician
Patient
Physician_ID
Patient_ID
Specialty
Admits
Patient_Name
Treatment_Detail or
(Physican_Patient)
Physician_ID
Patient_ID
Date
Time
Results
*Note that the “KEY” to
Treatment_Detail can be: Pat_ID and
Phys_ID (CK)