Comparer les valeurs de deux colonnes d'une table

select t1.IMSI, t1.MDN, t2.NUMF
from nomtable t1
inner join (
    select distinct NUMF from nomtable
) t2 ON SUBSTRING(t2.NUMF, -7) = SUBSTRING(t1.IMSI, -7)

    <?php	
set_time_limit(0);
error_reporting(E_ALL ^ E_NOTICE);

	//Connexion à la BD
mysql_connect('localhost','root','');
mysql_select_db('gestnum');

$sql = 'select t1.IMSI, t1.MDN, t2.NUMF
from coordab t1
inner join (
    select distinct NUMF from numero
) t2 ON SUBSTRING(t2.NUMF, -7) = SUBSTRING(t1.IMSI, -7)';

// on lance la requête (mysql_query) et on impose un message d'erreur si la requête ne se passe pas bien (or die)
$req = mysql_query($sql) or die('Erreur SQL !<br />'.$sql.'<br />'.mysql_error());
$i=0; 
// on va scanner tous les tuples un par un
while ($data = mysql_fetch_array($req)) 
    {
	$i++; 
	// on affiche les résultats
	echo 'IMSI : '.$data['IMSI'].'<br />';
	echo 'MDN : '.$data['MDN'].'<br />';
	echo 'NUMF : '.$data['NUMF'].'<br /><br />';
    }
mysql_free_result ($req);
mysql_close ();

?>

Erreur SQL !
select t1.IMSI, t1.MDN, t2.NUMF from coordab t1 inner join ( select distinct NUMF from numero ) t2 ON SUBSTRING(t2.NUMF, -7) = SUBSTRING(t1.IMSI, -7)
Unknown column 'NUMF' in 'field list'

 
-- phpMyAdmin SQL Dump
-- version 4.0.4
-- http://www.phpmyadmin.net
--
-- Client: localhost
-- Généré le: Jeu 13 Mars 2014 à 14:15
-- Version du serveur: 5.6.12-log
-- Version de PHP: 5.4.12
 
SET SQL_MODE = "NO_AUTO_VALUE_ON_ZERO";
SET time_zone = "+00:00";
 
 
/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */;
/*!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS */;
/*!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION */;
/*!40101 SET NAMES utf8 */;
 
--
-- Base de données: 'gestnum'
--
CREATE DATABASE IF NOT EXISTS 'gestnum' DEFAULT CHARACTER SET latin1 COLLATE latin1_swedish_ci;
USE 'gestnum';
 
-- --------------------------------------------------------
 
--
-- Structure de la table 'coordab'
--
 
CREATE TABLE IF NOT EXISTS 'coordab' (
  'ida' int(10) NOT NULL AUTO_INCREMENT,
  'IMSI' char(15) NOT NULL,
  'MEID' char(14) NOT NULL,
  'ESN1' char(8) NOT NULL,
  'PUK1' char(8) NOT NULL,
  'AKY' char(16) NOT NULL,
  'MDN' char(13) NOT NULL,
  'NUMF' char(13) NOT NULL,
  PRIMARY KEY ('ida'),
  UNIQUE KEY 'coordab_IMSI' ('IMSI'),
  KEY 'ida' ('ida')
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=364552 ;
 
-- --------
 
--
-- Structure de la table 'numero'
--
 
CREATE TABLE IF NOT EXISTS 'numero' (
  'idnum' int(10) NOT NULL AUTO_INCREMENT,
  'num' char(13) NOT NULL,
  PRIMARY KEY ('idnum')
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=6 ;
 
 
/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;
/*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;
/*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;