Database session, remember user, cookies

[eluser]blitzneo[/eluser]
Hi there,

this is my first post, and just wanted to let you know I'm quite comfortable using CI so far. I've been able to make a 'complete' user registration and login system following the user guide, which I really appreciate the work you guys did on it. Very clear.

So, what I cannot really understand is the way sessions are stored in the database. I mean, how I can check whether that user is already signed in (logged in.. etc) or not ? Without using the database it's working. I can log in a registered user, logout, alter userdata, etc.

If I activate the option to store these in the database I'm just lost. I'm seeking a little bit of guidance through this, I'm quite curious about this session thing.

Thanks a lot for your time.