Exam (elaborations)
COMP 353 DATABASE MANAGEMENT SYSTEMS SOLUTIONS MANUAL CONCORDIA UNIVERSITY
- Course
- COMP 353
- Institution
- Concordia University ( )
COMP 353 DATABASE MANAGEMENT SYSTEMS SOLUTIONS MANUAL CONCORDIA UNIVERSITY
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COMP 353 DATABASE MANAGEMENT SYSTEMS SOLUTIONSMANUAL CONCORDIA UNIVERSITY
Ra ghu Ra makrishna n et al.
Unive rsity of Wisc onsin
Madiso n, WI, USA
, 2
THE ENTITY-RE LATIONSHIP MODEL
Exercise 2.1 Explain the following terms briefly: attribute, domain, entity, relation- ship,
entity set, relationship set, one-to-many relationship, many-to-many relationship,
participation constraint, overlap constraint, covering constraint, weak entity set, aggre-
gation, and role indicator.
Answer 2.1 No answer provided yet.
Exercise 2.2 A university database contains information about professors (identified by
social security number, or SSN) and courses (identified by courseid). Professors teach
courses; each of the following situations concerns the Teaches relationship set. For each
situation, draw an ER diagram that describes it (assuming that no further constraints hold).
1. Professors can teach the same course in several semesters, and each offering must be
recorded.
2. Professors can teach the same course in several semesters, and only the most recent
such offering needs to be recorded. (Assume this condition applies in all subsequent
questions.)
3. Every professor must teach some course.
4. Every professor teaches exactly one course (no more, no less).
5. Every professor teaches exactly one course (no more, no less), and every course must
be taught by some professor.
6. Now suppose that certain courses can be taught by a team of professors jointly, but it
is possible that no one professor in a team can teach the course. Model this situation,
introducing additional entity sets and relationship sets if necessary.
Answer 2.2 Answer omitted.
5
,6 CHAPTER 2
Exercise 2.3 Consider the following information about a university database:
Professors have an SSN, a name, an age, a rank, and a research specialty.
Projects have a project number, a sponsor name (e.g., NSF), a starting date, an ending
date, and a budget.
Graduate students have an SSN, a name, an age, and a degree program (e.g., M.S.
or Ph.D.).
Each project is managed by one professor (known as the project’s principal inves-
tigator).
Each project is worked on by one or more professors (known as the project’s co-
investigators).
Professors can manage and/or work on multiple projects.
Each project is worked on by one or more graduate students (known as the project’s
research assistants).
When graduate students work on a project, a professor must supervise their work on
the project. Graduate students can work on multiple projects, in which case they will
have a (potentially different) supervisor for each one.
Departments have a department number, a department name, and a main office.
Departments have a professor (known as the chairman) who runs the department.
Professors work in one or more departments, and for each department that they work
in, a time percentage is associated with their job.
Graduate students have one major department in which they are working on their
degree.
Each graduate student has another, more senior graduate student (known as a
student advisor) who advises him or her on what courses to take.
Design and draw an ER diagram that captures the information about the university. Use
only the basic ER model here, that is, entities, relationships, and attributes. Be sure to
indicate any key and participation constraints.
Answer 2.3 The ER diagram is shown in Figure 2.1.
Exercise 2.4 A company database needs to store information about employees (iden- tified
by ssn, with salary and phone as attributes); departments (identified by dno, with dname
and budget as attributes); and children of employees (with name and age as attributes).
Employees work in departments; each department is managed by an
, The Entity-Relationship Model
age speciality pid start_date
work_in
ssn rank sponsor end_date
budget
Figure 2.1
Professor Manages project
ER Diagram for Exercise 2.3
Work_dept Runs
Supervises
Work_proj ssn
pc_time Dept Major senior
Graduate Advisor
grad
dno office
name
ssn
dname
age deg_prog
7
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