数据库设计-存储要求

Question

Suppose we want to store university courses and their entry requirements in a database. So for example BSc Mathematics, BSc Fine Art, MSc Computer Science etc.

Each course has it's own set of requirements, and might have a different number of non-shared requirements. For example, to be eligible for the BSc Maths you might need a A in Maths and a B in Physics. Whereas the BSc Fine Art might require a A in Art and that the user has a portfolio. The MSc might have a minimum age of 25 etc.

Suppose we then have a student who has his own set of attributes. So they might have a A in Maths and a B in Physics and a C in Chemistry and be of age 19.

How can we structure our database such that it is geared towards efficient lookups. And given a student's attributes how can we retrieve all the courses which they are eligible for?

On an abstract level we are looking for all items whose requirements are a subset of the attributes given.

I'd like to implement this in MySQL. The schema could be:

courses

id

name

requirements

course_id

subject

grade

But then how to do query the table to get all eligible courses when the student has a A in Subject 1, a B in Subject 2 etc.

For a course to be a match, each one of its requirements must be satisfied.

Thanks in advance, I hope my explanation isn't too confusing.

Answer 1

Okay. I think you need a subject list, with a bunch of subject id's.

Now, for the query, you will start with (or generate) a bunch of subject id's and grades. The easiest thing to do is to make this into a temporary table with those columns.

Now, you can do your query, joining the subject id's, and adding a "where temp.grade <= course.grade.

The trick to this is to count the rows. If it has the same number of rows as the course has specified, then you have a successful match.

Is that enough to get you going?