Database Design for Time Table Generation - mysql

Question

I am doing a project using J2EE(servlet) for Time Table Generation of College.
There are Six Slots(6 Hours) in a Day
4 x 1 HR Lectures
1 x 2 HR Lab
There Are three batches ( 3IT, 5IT, 7IT)
2 Classroom
1 LAB
Each slot in the time table will have
(Subject,Faculty)
For Lab I will duplicate the slot.
The Tables
Subject(SubjectID INT, SubjectName VARCHAR);
Faculty(FacultyID INT,FacultyName VARCHAR,NumOfSub INT,Subjects XYZ);
Here I am not able to decide the DATATYPE for subject. What should I do ? Since a faculty can teach multiple subjects ? Also how to link with Subject Table ?
P.S. Using MySQL Database

Answer 1

You don't want to actually store either NumOfSub (number of subjects) OR Subjects in Faculty. Storing subjects that way is a violation of First Normal Form, and dealing with it would cause major headaches.
Instead, what you want is another table:
FacultySubject
----------------
FacultyId -- fk for Faculty.FacultyId
SubjectId -- fk for Subject.SubjectId
From this, you can easily get the count of subjects, or a set of rows listing the subjects (I believe MySQL also has functions to return a list of values, but I have no experience with those):
This query will retrieve the count of Subjects taught by a particular teacher:
SELECT Faculty.FacultyId, COUNT(*)
FROM Faculty
JOIN FacultySubject
ON FacultySubject.FacultyId = FacultyId.FacultyId
WHERE Faculty.FacultyName = 'Really Cool Professor'
GROUP BY Faculty.FacultyId
... and this query will get all the subjects (named) that they teach:
SELECT Subject.SubjectId, Subject.SubjectName
FROM Faculty
JOIN FacultySubject
ON FacultySubject.FacultyId = FacultyId.FacultyId
JOIN Subject
ON Subject.SubjectId = FacultySubject.SubjectId
WHERE Faculty.FacultyName = 'Really Cool Professor'
(note that this last returns the subjects as a set of rows ie:
SubjectId SubjectName
=========================
1 Tree Houses
2 Annoying Younger Sisters
3 Swimming Holes
4 Fishing
)