Re: How would i do this?

Hello John,

You would really have to read-up on relational theory. There is a lot to be
found on the web. And if a take a peek at our books I see: Date, C.J., An
Introduction to DATABASE SYSTEMS.

But for a quick explenation: think in relations. Think in on of these posible
relations:
x has ZERO or ONE y  (example in a hospital setting: a patient x has zero or one
cause of death y)
x has ZERO to MORE y (example: a student x has followed zero to more classes y)
x has ONE to MORE y
x has ZERO to MORE y, AND, y has ZERO to MORE x (example teachers x that teach
to students y.... a teacher can have multiple students and a student can have
multiple teachers).


One piece of your example can be modeled like this:
A Class is comprised of students:
- you'd have a table that identifies classes:
class (class_id, class_name, ..other items that you'd like to record....)
- and a table that identifies students:
student (student_id, student_name, student_adres.............)
- and a table that lists which student attends which classes:
students_attending_classes (students_attending_classes_id, class_id,
student_id,......... )

Because the last table has multiple rows with one student in it, a student can
attend multiple classes, and a class can be attended by multiple students. If a
student can attend _only_ one class then you'd put the class_id in the
student-table.

But... there is A LOT to know... You can normalise into the 3rd, 4th or 5th
form, etc. etc. etc so I'd suggest you'd find some sites / literature.

Succes,
Arian.

John Hughes schreef:

> I am new to DB programming, so im not too sure about how to implement my DB.
>
> Here is what i need: a DB with tables of:
>
> 1. Students.
> 2. Classes
> 3. Teachers
> 4. Assignments
>
> Each teacher can be assigned a class, which is compromised of a list of
> students. Each class can be given assignments.
>
> Coming from a programming background, I could do this in c++ very easily. I
> actually started inmplementing it in a similar fasion: each student class
> teacher ect would have a uniqe id in the database, and, for example, a
> class would include an array of integer student id's.
>
> This seems really error prone, and not very efficient.
>
> what is a better implementation?
>
> John Hughes