How to get OnlineUsers with a second user info table.

Hi All,
1.I am using standard asp.net membership provider, 
2. I have a table which lots of extra column for extra user information. I have UserName column as primary key in new table.
3. I would like to get only online users with some columns from second table.  I do not know how to connect those 2 table. 
4. then I want to show it in gridview. 
Could you please tell me how to do it? Any code sample for me?

Thanks a lot.  
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