Question

I have finished designing the tables structures for a school course catalog. I am using four tables majors, courses, course_hours, course_date. Below I have detailed the components of each table. Some of the tables will use indexing based on course_id. I am new with database and struggling with building these tables inside my database. How can I make these tables link together with using course_id? Or is there a better way to structure these tables for my purpose. If possible providing a query to create these tables will be great.

Hopefully I am using the righ type(int,varchar, text, etc) for my variables.

Example of table courses

id serial
course_name varchar
course_code varchar
description text

Example of table course_dates (using index)

id int
course_id int
year date
semester int

Example of table course_hours (using index)

id int
course_id int
hours int

Example of table majors (one to many relationship- index)

 major_id int
 course_id int 
 major_name varchar

So a populated database would contain the following:

Table courses

course_id course_code course_name       course_description
1     INF1000     Visual Studio I   "Basic programming"
2     INF1001     Visual Stuido II  "More programming"

Table course_dates (0 for spring, 1 for fall, 2 all year)

id course_id year semester
1  1         2012 0
2  1         2013 1
3  2         2013 1

Table course_hours

id course_id course_hours 
1  1         3 
2  1         4 
3  2         4 

Table majors

id course_id major_name
1  1         Computer Engineering 
2  1         Information Systems 
3  2         Network Administrator

Answer 1

i would do some restructuring:

• add hours to courses and get rid of course_hours table (i don’t see
  any advantage to extracting hours to a seperate table)
• course_dates might be better named as semester and the fields would be year (int) and semester (int)
• majors should just explain each major so take course_id out and put it into a xref table
• rename all tables to singular form (just a style preference)

giving you a structure like:

edit: made it back to a mysql box. here’s the script for this structure. remember you might want to change charset and engine type as those can change per database, these are probably fine as is for default

CREATE TABLE IF NOT EXISTS `course` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(100) NOT NULL,
  `code` varchar(10) NOT NULL,
  `description` varchar(500) DEFAULT NULL,
  `hours` tinyint(6) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;

CREATE TABLE IF NOT EXISTS `course_semester_xref` (
  `course_id` int(11) NOT NULL,
  `semester_id` int(11) NOT NULL,
  PRIMARY KEY (`course_id`,`semester_id`),
  KEY `semester_id` (`semester_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

CREATE TABLE IF NOT EXISTS `major` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(50) NOT NULL,
  `description` varchar(500) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;

CREATE TABLE IF NOT EXISTS `major_course_xref` (
  `major_id` int(11) NOT NULL,
  `course_id` int(11) NOT NULL,
  PRIMARY KEY (`major_id`,`course_id`),
  KEY `course_id` (`course_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

CREATE TABLE IF NOT EXISTS `semester` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `year` smallint(6) NOT NULL,
  `semester` tinyint(4) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;

ALTER TABLE `course_semester_xref`
  ADD CONSTRAINT `course_semester_xref_ibfk_2` FOREIGN KEY (`semester_id`) REFERENCES `semester` (`id`),
  ADD CONSTRAINT `course_semester_xref_ibfk_1` FOREIGN KEY (`course_id`) REFERENCES `course` (`id`);

ALTER TABLE `major_course_xref`
  ADD CONSTRAINT `major_course_xref_ibfk_2` FOREIGN KEY (`course_id`) REFERENCES `course` (`id`),
  ADD CONSTRAINT `major_course_xref_ibfk_1` FOREIGN KEY (`major_id`) REFERENCES `major` (`id`);