How to get logged online users?

Question

How to get logged users from SharePoint Content Database?

Or in the other hand, What is the best practice to Making OnLine Logged users WebPart in SharePoint?

Answer 1

This will get you started: Find Number of Users Currently Logged on to a SharePoint Site

Although the blog post is aimed at SharePoint 2007, it should be feasible to make a SharePoint 2010 version of it.