how use ajax select list

hey,
i have question,
this is my page

<?php
// Template Name: annuaire
get_header();
get_sidebar('sidebar_ac');
?>

<form>
country:
<select name="country" id="country" >
  <option value=""></option>
  <option value="1">USA</option>
  <option value="2">ENGLAND</option>
  <option value="3">JAPAN</option>

</select>
center:
<select name="commune" id="commune">
  <option value=""></option>
  <option value="1">Washington</option>
  <option value="2">London</option>
  <option value="3">Tokio</option>
</select>

Cycle:
<select name="place" id="place" onchange ="showEtab(document.getElementById('country').value,document.getElementById('commune').value,document.getElementById('place').value)">
  <option value=""></option>
  <option value="1">AMERICA</option>
  <option value="2">EUROP</option>
  <option value="3">ASIA</option>
</select>

</form>
<?php get_footer(); ?>

this ismy request in function.php:

$sql="SELECT * FROM pays WHERE country='$wilaya' and commune='$commune' and place='$place'";

how i can use ajax to load the result

[Moderator note: code fixed. Please wrap code in the backtick character or use the code button.]