Efficient MySQL Database Design - mysql

Question

I'm working on a small program for my school and I have a question about the following DB design.
The admin will assign subjects to teachers via an online form.
An example of a subject would be something like:
Subject Field 1: (Grade 5 Math: Teaching 5/1, 5/2 and 5/3) [Text Field]
Subject Field 2: (Grade 6 Math: Teaching 6/2 and 6/6) [Text Field]
I have added 7 subjects fields per their request as there won't be anyone that will exceed 7 subjects.
Each Subject Field will have required things to complete such as lesson plans, course syllabus etc...
Each requirement will have the following requirements:
Language (Language 1, Language 2 or Both) [Drop Down]
Type (Printed, File or Both) [Drop Down]
Time (Semester 1, Semester 2 or both) [Drop Down]
So far I have come up with this DB design:
ID (Primary, Auto Incremented)
TID (Teacher ID)
Year
Subject1
Subject1Requirement1
Subject1Requirement2
Subject1Requirement3
TimeSent
TimeReviewed
Subject2
Subject2Requirement1
Subject2Requirement2
Subject2Requirement3
TimeSent
TimeReviewed
Subject3
Subject3Requirement1
Subject3Requirement2
Subject3Requirement3
TimeSent
TimeReviewed
Continued to Subject 7.
I feel that there is a more efficient way of doing it but just can't think of a better way.
Thanks.

Answer 1

If there's no relationship between teacher's subjects, you can design 3 tables like the following
Teachers TeacherSubjects SubjectRequirements
---------- --------------- --------------------
ID SubjectID ----> SubjectID
TID --\ SubjectName SubjectRequirement
Year \--> TID Language
TimeSent Type
TimeReviewed Time
In such design
Each teacher can have multiple subjects (not limited to 7 subjects)
Each teacher's subject have multiple requirements (not limited to 5 requrirements)
Sample data
INSERT INTO Teachers(ID, TID, Year) VALUES (1,'LiuYan', 2012);
INSERT INTO Teachers(ID, TID, Year) VALUES (2,'Emily', 2012);
INSERT INTO TeacherSubjects (SubjectID, SubjectName, TID) VALUES ('SubjectID_1', 'SubjectName1', 'LiuYan');
INSERT INTO TeacherSubjects (SubjectID, SubjectName, TID) VALUES ('SubjectID_2', 'SubjectName2', 'LiuYan');
-- ...
INSERT INTO TeacherSubjects (SubjectID, SubjectName, TID) VALUES ('SubjectID_N', 'SubjectNameN', 'LiuYan');
INSERT INTO TeacherSubjects (SubjectID, SubjectName, TID) VALUES ('SubjectID_N+1', 'SubjectName N+1', 'Emily');
INSERT INTO TeacherSubjects (SubjectID, SubjectName, TID) VALUES ('SubjectID_N+2', 'SubjectName N+2', 'Emily');
-- ...
INSERT INTO TeacherSubjects (SubjectID, SubjectName, TID) VALUES ('SubjectID_M', 'SubjectName M', 'Emily');
INSERT INTO SubjectRequirements (SubjectID, SubjectRequirement, Language, Type, Time) VALUES ('SubjectID_1', 'Curriculum', 'Language 1', 'Printed', 'Semester 1');
INSERT INTO SubjectRequirements (SubjectID, SubjectRequirement, Language, Type, Time) VALUES ('SubjectID_1', 'Course Syllabus', 'Language 2', 'File', 'Semester 2');
INSERT INTO SubjectRequirements (SubjectID, SubjectRequirement, Language, Type, Time) VALUES ('SubjectID_1', 'Learning Management', 'Both Language', 'Both Type', 'Both Semester');
--...
INSERT INTO SubjectRequirements (SubjectID, SubjectRequirement, Language, Type, Time) VALUES ('SubjectID_N+1', 'Curriculum', 'Language 2', 'Both Type', 'Semester 2');
--...

Answer 2

On of the key aspects of database is having relationships (links) between tables - so that if a table (row) needs to refer to something else that is different then use another table and link together with foreign keys - this table, in our case TeacherSubject is a junction table
To give you a brief look of how I'd implement your requirements I think we need three tables, and the SubjectsTeacher below is a linking table to join the two.
You define each subject and teacher and then add entries to the TeacherSubject table to associate teachers with subjects.
To create the database:
CREATE TABLE `Subject` (
`SID` INTEGER NOT NULL AUTO_INCREMENT ,
`Name` VARCHAR(100) NOT NULL ,
`Curriculum` INTEGER NOT NULL ,
`Syllabus` INTEGER NOT NULL ,
`LearnManagement` INTEGER NOT NULL ,
`Individual Analysis` INTEGER NOT NULL ,
PRIMARY KEY (`SID`)
);
CREATE TABLE `Teachers` (
`TID` INTEGER NOT NULL AUTO_INCREMENT ,
`Name` VARCHAR(100) NOT NULL ,
PRIMARY KEY (`TID`)
);
CREATE TABLE `TeacherSubject` (
`id` INTEGER NOT NULL AUTO_INCREMENT ,
`SID_Subject` INTEGER NOT NULL ,
`TID_Teachers` INTEGER NOT NULL ,
PRIMARY KEY (`id`)
);
Then add the foreign keys that tells the database how your fields are linked - this step is important as it will ensure that you maintain data integrity and cannot insert bad data into this data.
ALTER TABLE `TeacherSubject` ADD FOREIGN KEY (SID_Subject) REFERENCES `Subject` (`SID`);
ALTER TABLE `TeacherSubject` ADD FOREIGN KEY (TID_Teachers) REFERENCES `Teachers` (`TID`);
Then setup a few rows for test.
INSERT INTO `Subject` (`SID`, `Name`, `Curriculum`, `Syllabus`, `LearnManagement`, `Individual Analysis`) VALUES
(1, 'Subject1', 1, 2, 3, 4),
(2, 'Subject1', 1, 2, 3, 4),
(3, 'Subject2', 1, 2, 3, 4),
(4, 'Subject3', 1, 2, 3, 4),
(5, 'Subject4', 1, 2, 3, 4);
INSERT INTO `Teachers` (`Name`) VALUES ('Teacher 1');
INSERT INTO `Teachers` (`Name`) VALUES ('Teacher 2');
INSERT INTO `TeacherSubject` (`id`, `SID_Subject`, `TID_Teachers`) VALUES
(1, 1, 1),
(2, 2, 1),
(3, 3, 2),
(4, 4, 2),
(5, 1, 2);
And finally to find out which subject teacher#1 has:
select * from TeacherSubject
INNER JOIN Teachers on TID=TID_Teachers
WHERE TID_Teachers=1