cs327e Lab3 Solution

# The University of Texas

CS 327e

Fall 2004

### Lab 3 Solution

PURPOSE:

The purpose of this lab is to learn about Normalization and good database design.

IMPLEMENTATION:

For this lab, consider solving ALL of the following:

A) Consider a relation that involves STUDENT CLASS GRADE data. Specifically, consider the relation

STUDENT_CLASS_GRADE (CourseNumber, CourseDesc, CourseFee, ClassUniqueNumber, ClassTime, ClassMaxStudentsAllowed, ClassRoom, LetterGrade, StudentEID, StudentFirstName, StudentLastName, ProfessorFirstName, ProfessorLastName, ProfessorEID, DepartmentName, DepartmentSchool).

Where PK = (StudentEID, ClassUniqueNumber)

As you might guess, this will result in a highly denormalized relational data. Your job is to normalize the above relation.

You can assume the following:

1) This is information for 1 semester (say Fall 2004) in a university environment like The University of Texas.

2) A Course may have 1 or more sections (or classes); each section belongs to only 1 course. Each section has a unique number that is unique across all courses for this semester.

3) A professor may teach 1 or more (up to 3) sections, but a section is taught by exactly 1 professor.

4) Domain values for LetterGrade are {A, B, C, D, F, Q, I}

5) A student must be enrolled in a minimum of 3 different courses, with a maximum of 7.

6) StudentEID uniquely identifies each student; ProfessorEID uniquely identifies each professor; ClassUniqueNumber uniquely identifies each class; CourseNumber uniquely identifies each course.

7) Examples of CourseNumber are {CS301K, PH301, CS302, CS303E, CS327E etc.}

8) Examples of ClassUniqueNumber are {53635, 53640, 53650, 53655 etc.}

9) A Department can have 1 or more students and 1 or more professors. Each professor (or student) belongs to exactly 1 department.

10) Assume that there are at least 50,000 students and 500 professors in the university.

11) Each School (or College) can have 1 or more departments, but a department always belongs to a school (College). As an example, the department of computer sciences belongs to the college of natural sciences.

For this relation,

A) Identify all functional dependencies (FD’s). (HINT: I can see at least 5 Functional Dependencies).

B) Break this relation down into relation(s) that are in 2nd Normal Form (NF). Clearly state the FD’s and primary key for each of these relations.

C) Break the above relation(s) into 3rd NF. Clearly state the FD’s and primary key for each of these relations.

D) For the relations in C), clearly state the referential integrity constraints (FK-PK relationships).

In all of the above, CLEARLY STATE ANY ADDITIONAL ASSUMPTIONS THAT YOU MIGHT HAVE MADE.

B) For the relations in 3rdNF above, draw the ER diagram. Clearly label all PK, FK, entity names, relationship names, attribute names, and the referential integrity actions (e.g. delete cascade etc.).

In all of the above, CLEARLY STATE ANY ADDITIONAL ASSUMPTIONS THAT YOU MIGHT HAVE MADE.

SOLUTION

A)

STUDENT_CLASS_GRADE (CourseNumber, CourseDesc, CourseFee, ClassUniqueNumber, ClassTime, ClassMaxStudentsAllowed, ClassRoom, LetterGrade, StudentEID, StudentFirstName, StudentLastName, ProfessorFirstName, ProfessorLastName, ProfessorEID, DepartmentName, DepartmentSchool).

Where PK = (StudentEID, ClassUniqueNumber)

For discussion purposes, let’s rewrite the above relation as

R1 (A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P).

Where

A = CourseNumber,

B = CourseDesc,

C = CourseFee,

D = ClassUniqueNumber,

E = ClassTime,

F = ClassMaxStudentsAllowed,

G = ClassRoom,

H = LetterGrade,

I = StudentEID,

J = StudentFirstName,

K = StudentLastName,

L = ProfessorFirstName,

M = ProfessorLastName,

N = ProfessorEID,

O = DepartmentName,

P = DepartmentSchool

And PK = (D,I)

From the assumptions and constraints, we can determine the following FDs:

FD1R1: D,I à A,B,C,E,F,G,H,J,K,L,M,N,O,P

FD2R1: I à J,K,O,P

FD3R1: N à L,M,O,P

FD4R1: A à B,C

FD5R1: D à A,E,F,G,N

FD6R1: O à P

a) FD2R1 and FD5R1 violate 2NF since they are partial dependencies.

Hence, separating them into independent relations gives us:

R1R2 (I,J,K,O,P)

With

FD2R1R2: I à J,K,O,P

FD6R1R2: O à P

R1R3 (D,A,B,C,E,F,G,L,M,N,O,P)

With

FD14R1R3: D à A,B,C,E,F,G,L,M,N,O,P

FD3R1R3: N à L,M,O,P

FD4R1R3: A à B,C

R1R4 (D,H,I)

With

FD1R1R4: D,I à H

Since there are no partial dependencies in any of the above 3 relations, these relations are said to be in 2nd NF.

b)

The following FD’s are not in 3NF:

FD6R1R2: O à P (in R1R2)

FD3R1R3: N à L,M,O,P (in R1R3)

FD4R1R3: A à B,C (in R1R3)

Hence, breaking the respective relations gives us:

R1R2R5 (I,J,K,O)

With

FD2R1R2R5: I à J,K,O

R1R2R6 (O,P)

With

FD6R1R2R6: O à P

R1R3R7 (D,A,E,F,G,N)

With

FD14R1R3R7: D à A,E,F,G,N

R1R3R8 (N,L,M,O)

With

FD3R1R3R8: N à L,M,O

R1R3R9 (A,B,C)

With

FD4R1R3R9: A à B,C

R1R4 (D,H,I)

With

FD1R1R4: D,I à H

Notice that each of the above six relations are in 3rdNF. Rewriting these into appropriate names, we get the following relations with their respective FDs (also, I have written the appropriate FKs for each relation):

1) STUDENT (StudentEID, StudentFirstName, StudentLastName, DepartmentName)

FD1: StudentEID à StudentFirstName, StudentLastName, DepartmentName

FK1: STUDENT.DepartmentName is FK to DEPARTMENT.DepartmentName

2) DEPARTMENT (DepartmentName, DepartmentSchool)

FD2: DepartmentName à DepartmentSchool

3) CLASS (ClassUniqueNumber, CourseNumber, ClassTime, ClassMaxStudentsAllowed, ClassRoom, ProfessorEID)

FD3: ClassUniqueNumber à CourseNumber, ClassTime, ClassMaxStudentsAllowed, ClassRoom, ProfessorEID

FK2: CLASS.CourseNumber is FK to COURSE.CourseNumber

FK3: CLASS.ProfessorEID is FK to PROFESSOR.ProfessorEID

4) PROFESSOR (ProfessorEID, ProfessorFirstName, ProfessorLastName, DepartmentName)

FD4: ProfessorEID à ProfessorFirstName, ProfessorLastName, DepartmentName

FK4: PROFESSOR.DepartmentName is FK to DEPARTMENT.DepartmentName

5) COURSE (CourseNumber, CourseDesc, CourseFee)

FD5: CourseNumber à CourseDesc, CourseFee

6) GRADE (ClassUniqueNumber, LetterGrade, StudentEID)

FD6: StudentEID, ClassUniqueNumber à LetterGrade

FK5: GRADE.ClassUniqueNumber is FK to CLASS.ClassUniqueNumber

FK6: GRADE.StudentEID is FK to STUDENT.StudentEID