SQL Query Syntax

[DrussRob]

I've tried to get this to exclude certain forums from the list by adding NOT IN (1, 2, 3); and hiding private with "visible".
But is doesnt seem to be working right, can anyone see what I've maybe done wrong?

thx

PHP Code:

<?php
$threads = $db->query_read(" 
SELECT title, threadid FROM " . TABLE_PREFIX . "thread WHERE visible (<> 0) AND forumid (NOT IN (3, 4, 9))
LIMIT 0,6 
"); 
while ($thread = $db->fetch_array($threads)) 
{
    $title = $thread['title'];
    $threadid = $thread['threadid'];

    echo "<a href='forum/showthread.php?t=$threadid'>$title</a><br />";
} 
?>

also does "visible" control restricted threads to different usergroup?