There are a couple of ways to do this, depending on your Visualizer. If you are using the Grid Visualizer then you need to place it in your SQL, if you are using the HTML Visualizer it is a little easier. Essentially, you need to go to the user profile page for any user and get the URL. Then figure out where the UserID is (I don't have a DNN installation handy at the moment, so I don't have the exact URL format on hand).
For this post, I will assume that it is:
http://mydnnsite.com/path/to/profile/[UserID goes here]/page/Default.aspx
If you are using the Grid Visualizer, then you can put something like this in your SQL
SELECT '<a href="http://mydnnsite.com/path/to/profile/' + UserID + '/page/Default.aspx">User Profile</a>' as ProfileLink, ...
This will build the complete <a> tag in the SQL Server.
If you are using the HTML Visualizer, it is a lot easier, just add the link to your HTML template and use the "[UserId]" token (or replace "UserId" with the name of the column returned by your query that contains the User ID). For example:
<a href="http://mydnnsite.com/path/to/profile/[UserId]/page/Default.aspx">[UserName]'s Profile</a> ...
You can also use the XSLT Visualizer, but I won't go in to details regarding that. The concept is similar to the HTML Visualizer though, just build the link inside the template.