Probleme d'insert avec php5.3 et mysql 5.1

$sql = "SELECT * FROM temp_ville ";
$sql = mysql_query($sql);

while ( $data = mysql_fetch_array($sql)){
	
		echo $sql_up = "UPDATE ville_assign  SET zone = '".$data['assign']."' WHERE ville_assign  = '".$data['ville']."'";
		$sql_up = mysql_query($sql_up);
		
		$sql_sel = "SELECT * FROM ville_assign where ville_assign  ='".$data['ville']."'";
		$sql_sel = mysql_query($sql_sel);
		
		if (mysql_num_rows($sql_sel) ==0){
		
	echo $data['ville']."-".$data['assign']."<br />";
	echo sql2 = "INSERT INTO ville_assign (id_assign, ville_assign, cp, villetrajID, zone) values ('', '', '', '1', '".$data['assign']."')";
		$sql2 = mysql_query($sql2);
		}
}