Best way to retrieve the number of users with a specific secondary usergroup?

[Attilitus]

Is there any easy way to retrieve the amount of users who have a specific secondary usergroup? I need to be able to quickly retrieve a count, and want to know the most load-friendly way of doing it. (Without looping through the resultset to check if the groupid is in the array of membergroupids.)

Edit: for other people's reference here is how vbulletin does it:

(I guess I'm all set.)

	// count secondary users
	$groupcounts = $db->query_read("
		SELECT membergroupids, usergroupid
		FROM " . TABLE_PREFIX . "user
		WHERE membergroupids <> ''
	");
	while ($groupcount = $db->fetch_array($groupcounts))
	{
		$ids = fetch_membergroupids_array($groupcount, false);
		foreach ($ids AS $index => $value)
		{
			if ($groupcount['usergroupid'] != $value AND !empty($vbulletin->usergroupcache["$value"]))
			{
				$vbulletin->usergroupcache["$value"]['secondarycount']++;
			}
		}
	}