Question

For the site I’m working on, I want a user to have the ability to checkmark multiple boxes that represent things he/she might be interested, similar to StumbleUpon. A user would check ‘web development’ and ‘web design’ then click ‘Submit’, which would then store his preferences in a database.

Later, if somebody created a project that was tagged with one of the preferences he selected, that user would get an update. So if I made a new project that said “Building a Website” and checked the category “web development”, all users who had “web development” selected on their personal profiles would get some kind of message or email alerting them to the newly created topic.

What is the best way to implement this in MySQL format? I looked at some pages on managing hierarchical data (there will be generalized categories like “Computers” or “Music” and an admin will be able to add/delete/edit categories), but none of the methods seemed to be what I needed – at least, not in the way of thinking I’m stuck in. Perhaps there’s an easier answer out there that I’ve been overlooking?

Answer 1

Create a table containing the various interests. Say

Interests :- id, interest

Then a table which stores all the interests selected by a user as

UserInterests :- user_id, interest_id

And a project interest relation as

ProjectInterest :- project_id, interest_id

Now when a new project is added you can run a query similar to the following onw to get the users that the project is of interest

SELECT DISTINCT user_id
FROM UserInterests ui, ProjectInterests pi 
WHERE ui.interest_id = pi.interest_id AND pi.project_id = <new project id>

Or, using the explicit join syntax:

SELECT DISTINCT user_id
FROM UserInterests ui
  INNER JOIN ProjectInterests pi ON ui.interest_id = pi.interest_id
WHERE pi.project_id = <new project id>