if you want to see the actual query do this:
$query = "select user_id from sv_users where user_name='$username';";
$id = mysql_query($query) or die(mysql_error());
echo $query;
and then if you want to see the info from that, you need to use [man]mysql_fetch_array[/man], [man]mysql_fetch_object[/man], or others to, like it says, fetch the results