<?php
.....connexion ici
$sql = "SELECT * FROM ta_table WHERE blabla";
$req = mysql_query($sql) or die('Erreur SQL !<br>'.$sql.'<br>'.mysql_error());
?>
<select>
<?php
while($xxx = mysql_fetch_assoc($req))
{
echo "<option value=\"".$xxx['ton_champ']."\">".$xxx['ton_champ']."</option>";
}
?>
</select>