PHP isUnique

// FUNCTION isUnique
//
// $table -> table to check
// $field -> column to check
// $value -> value to check
// $except -> a clause to add to the mix.
//
// ex if( ! isUnique( "users" , "user_login" , "user1" );
// ex if( ! isUnique( "users" , "user_login" , "user1" , "user_id != XX" );
 
function isUnique( $table , $field , $value , $except = null )
{
 
 
        // build the query
        // value is escape cause maybe that comes from the user form
        // the rest should be coming from the programmer.
 
        $q = "SELECT COUNT( ".$field." ) as total FROM ".$table." WHERE ".$field." = '".mysql_escape_string( $value )."'";
 
 
        // ok exception clause so lets just add it to the where
        // this probably gets used when a user does an update to their
        // user name...
	if( $except != null )
	{
              $q .= "' AND ".$except;
	}
 
 
	$qr = dbquery( $q );
	$total = $qr->fields['total'];
 
	return $total == 0;
}