Customer Portal - Customer Portal ID matching up to Database ID

I am looking at Zoho to create an idea I have in mind. I'd like to find out if the features I need are available before I sign up. Perhaps I may be thinking about this wrong but I am perceiving the customer portal, and the users (persons) in that, as a separate entity from the people in my database - but they are one in the same in my app and the person in the customer portal must be able to access his/her info in my database...is there a way to do this currently? Let me explain:

My database will be a mass collection of test scores. These test scores will be collected at ongoing events by me and entered into the database by me. I will grant access (for a fee) to my customers (the people who took the tests) so they can view their scores, see their progress over time, and see how they compare to other test takers in the database via a dashboard.

So...

1) I need to be able to match the user in the database to the user accessing it through the customer portal
2) I need to produce their results within the database through reports on a dashboard
3) I want to keep other users particular data private, but want to use their data to calculate averages, high low scores, standard deviation to display how the user stacks up to all other test takers in database.
4) This data should be able to be narrowed down...for instance, user test score vs. all test scores, user test score vs. test score within age group, user test score within age group from same region of country etc....

Possible with Zoho creator???

Thank you for your time.