Enfin si le numero matricule est numerique, la requete suivante serait plus appropriee:

$result =mysql_query ("SELECT * FROM $table WHERE assoc=$num OR un=$num OR deux=$num OR trois=$num ORDER BY assoc, lastName, firstName, school " );

En esperant t'avoir aide.

$result =mysql_query ("SELECT * FROM $table WHERE assoc LIKE '$num' ORDER BY assoc, lastName, firstName, school " )

$result =mysql_query ("SELECT * FROM $table WHERE assoc LIKE '$num' OR un LIKE '$num' OR deux LIKE '$num' OR trois LIKE '$num' ORDER BY assoc, lastName, firstName, school " );

if(!mysql_num_rows( $result ))
        echo "d'ou ki sort cet eleve...";
else
{
        if($row['assoc'])
                echo "l'est dans cette ecole";
        if($row['un'])
                echo "l'est dans celle-ci"; 
        if($row['deux'])
                echo "l'est dans celle-là";
        //etc...
}

$result =mysql_query ("SELECT * FROM $table WHERE assoc=$num OR un=$num OR deux=$num OR trois=$num ORDER BY assoc, lastName, firstName, school " );

<?php
$num = $_POST[ "snum" ];
$table = "_annuaire";
include 'key.php' ;
mysql_connect( $host ,$user ,$pass) or die( "cannot connect " .mysql_error () ); 
mysql_select_db( $db ) or die( "cannot select db " .mysql_error () ); 
$result =mysql_query ("SELECT * FROM $table WHERE assoc LIKE '$num' ORDER BY assoc, lastName, firstName, school " ) or die ( "select error " .mysql_error () ); 
if ( mysql_num_rows( $result ) > 0) {
while ($row =mysql_fetch_array ($result ) ) {
$flashstr .= $row ["assoc" ]." : ".$row ["lastName" ]." ".$row ["firstName" ]."  ".$row ["school" ]."-".$row ["promo" ]."<br />";
}
print ("&erreur=Cette liste n'est pas cliquable."."&compte=".mysql_num_rows($result)."&listetotale=".urlencode($flashstr));
}
else
print ("&erreur=Aucun élève répertorié."."&compte="."&listetotale=");
?>