Database Reference
In-Depth Information
9. Suppose in addition to the requirements specified in Question 7, you must store the number of the department
in which the student is majoring. Indicate the changes this would cause in the design in the following two
situations:
a. The student must be assigned an advisor who is in the department in which the student is majoring.
b. The student's advisor does not necessarily have to be in the department in which the student is majoring.
10. Illustrate the physical-level design process by means of the design shown in Question 7. List the tables, identify
the keys, and list the special restrictions that programs must enforce.
11. Is the database design method top-down or bottom-up? How can you modify this method to gain the advan-
tages to both types of design methods?
12. Design a survey form of your own. Fill it out as it might have been completed during the database design for
Premiere Products. For any questions you have too little information to answer, make a reasonable guess.
13. Using a document at your own school (for example, a report card), determine the attributes present in the docu-
ment. Using your knowledge of the policies at your school, determine the functional dependencies present in the
document. Use these dependencies to create a set of tables and columns that you could use to produce the
document.
14. Describe the different ways of implementing one-to-one relationships. Assume you are maintaining information
on offices (office numbers, buildings, and phone numbers) and faculty (numbers and names). No office houses
more than one faculty member; no faculty member is assigned more than one office. Illustrate the ways of
implementing one-to-one relationships using offices and faculty. Which option would be best in each of the fol-
lowing situations?
a. A faculty member must have an office, and each office must be occupied by a faculty member.
b. A faculty member must have an office, but some offices are not currently occupied. You must maintain
information about the unoccupied offices in an Office relation.
c. Some faculty members do not have an office, but all offices are occupied.
d. Some faculty members do not have an office, but some offices are not occupied.
15. For each of the following collections of relations, give the assumptions concerning the relationship between stu-
dents, courses, and faculty members that are implied by the collection. In each relation, only the primary keys
are shown.
a. Student (StudentNum, CourseNum, FacultyNum)
b. Student (StudentNum, CourseNum)
Faculty (CourseNum, FacultyNum)
c. Student (StudentNum, CourseNum)
Faculty (CourseNum, FacultyNum)
StudentFaculty (StudentNum, FacultyNum)
d. Student (StudentNum, CourseNum, FacultyNum)
e. Student (StudentNum, CourseNum)
Faculty (CourseNum, FacultyNum)
StudentFaculty (StudentNum, FacultyNum)
16. Describe the relationship between columns that can be null and entity subtypes. Under what circumstances
would these columns lead to more than one entity subtype?
17. How is it possible to merge a collection of relations that is in third normal form into a cumulative design that is in
third normal form but not obtain a collection of relations that is in third normal form? Give an example other than
the one described in the text.
18. Describe the entity-relationship model. How are entities, relationships, and attributes represented in this model?
What is a composite entity? Describe the approach to diagrams that uses a crow's foot. Describe how you
would represent cardinality in an E-R diagram.
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