Insertion dans la base de donnée

Salut a tous,
SVP qui peut m'aider a trouver l'erreur dans ce code :
<?php
$cnx = mysql_connect("localhost","root","") or die("Unable to connect to database");
mysql_select_db("sitebd") or die( "Unable to select database");
$nom='';
if (isset($_POST["nom"])) {$nom=$_POST["nom"]; }
$prenom='';
if (isset($_POST["prenom"])) {$prenom=$_POST["prenom"];}
$mail='';
if (isset($_POST["mail"])) {$mail=$_POST["mail"];}
$num='';
if (isset($_POST["num"])) {$num=$_POST["num"];}
$password='';
if (isset($_POST["password"])) {$password=$_POST["password"];}
$classe='';
if (isset($_POST["classe"])) {$classe=$_POST["classe"];}
$section='';
if (isset($_POST["section"])) {$section=$_POST["section"];}
$semestre='';
if (isset($_POST["semestre"])) {$semestre=$_POST["semestre"];}
?>
<?php
mysql_connect("localhost","root","") or die("Unable to connect to database");
mysql_select_db("mabase") or die( "Unable to select database");

if(empty($num) OR empty($nom) OR empty($prenom) OR empty($password) OR empty($niveau) OR empty($section))
{
echo 'Veuillez remplir les champs: NumInscri, Nom, Prénom, password, niveau, section';
}
else
{
$sql1 = "INSERT INTO etudiant (Nom, Prenom, NumInscr, niveau, section, mail, password, classe, semestre)
VALUES( '$nom', '$prenom' , '$num', '$niveau' , '$section' , '$mail', '$password' , '$classe' , '$semestre') ";
$sql2 = "INSERT INTO authentification(login, pwd) VALUES ('$num','$password')";


$requete = mysql_query($sql1, $cnx) or die('Erreur SQL !'.$sql1.'<br>'.mysql_error());
mysql_query($sql2) or die('Erreur SQL !'.$sql2.'<br>'.mysql_error());

if($requete)
{
echo("L'insertion a été correctement effectuée") ;
}
else
{
echo("L'insertion à échouée") ;
}

mysql_close();
}
}
?>

<p>
<?php
mysql_free_result($Recordset1);
?>
</p>


Merci d'avance.