[Colin F]

You would have to make a small script, something like this:

PHP Code:

$threads = $DB_site->query("SELECT threadid,whoviewed FROM " . TABLE_PREFIX . "thread WHERE whoviewed != ''");
while ($thread = $DB_site->fetch_array($threads))
{
$vieweduserids = explode(" ", $thread['whoviewed']);
$changeduserids = implode(",", $vieweduserids);
$DB_site->query("UPDATE thread SET whoviewed = '$changeduserids' WHERE threadid = $thread[threadid]");
} 


You might have to change the explode part to fit whatever the data looks like now.