I am currently working on a stock market monitoring application and I was wondering if anyone cold help me by giving me a guideline on how to create a new portfolio(sort of a personal account) for each user that accesses the system such that 2 different users do not have the same portfolio.
I am making use of SQL server for my database if that comes in helpful. Thank you.

Is it not good enough to use user IDs or Portfolio IDs?

I am following you on that, but on the development part, is it that I create a new class for a portfolio and then call it up for each new account created