Need SQL help

[Matt]

UPDATE `mybb_users` SET `usergroup` = 'B' WHERE `usergroup` = 'A' AND `postnum` >= '1' AND `regdate` > '1296906752';

This'll move people who registered in the last 24 hours. Change the A and B to the IDs of the relevant usergroups.

Also it'd probably be a lot easier to use the promotions system to change their usergroups, rather than doing it manually...