any mysql query/command works in that screen.
You can start with say phpmyadmin.
which will show you the query on certain functions.
Or read the manual:
http://us2.php.net/manual/en/
It is not for the faint of heart.

For example if you wish to find people with more than 99 Private messages.
Enter the following in the screen.
SQL Query
SELECT COUNT(*) as PMs, u.USER_DISPLAY_NAME
FROM
ubbt_PRIVATE_MESSAGE_USERS pmu, ubbt_PRIVATE_MESSAGE_TOPICS pmt, ubbt_USERS u
WHERE pmu.TOPIC_ID=pmt.TOPIC_ID
AND pmu.USER_ID=u.USER_ID
GROUP BY pmu.USER_ID HAVING PMs>99
ORDER BY PMs DESC

Of course the ubbt prefix may need to be changed for your site.

Blue Man Group
There is no such thing as stupid questions. Just stupid answers