Solved: How can i implement my own mysql query into an JOOMLA 2.5 page

Must implement the following mySQL query-code into an Joomla Article:
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Here is my code example (the complete code is attached) this is the ->index.php

<?php
include('db.php');
include('func.php');
?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Chained Select Boxes using PHP, MySQL and jQuery</title>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3/jquery.min.js"></script>

<script type="text/javascript">
$(document).ready(function() {
      $('#wait_1').hide();
      $('#drop_1').change(function(){
       $('#wait_1').show();
       $('#result_1').hide();
$.get("func.php", {
            func: "drop_1",
            drop_var: $('#drop_1').val()
}, function(response){
$('#result_1').fadeOut();
setTimeout("finishAjax('result_1', '"+escape(response)+"')", 400);
});
      return false;
      });
});

function finishAjax(id, response) {
$('#wait_1').hide();
$('#'+id).html(unescape(response));
$('#'+id).fadeIn();
}
</script>
</head>

<body>
<p>
<form action="" method="post">

<select name="drop_1" id="drop_1">

<option value="" selected="selected" disabled="disabled">Select a Category</option>

<?php getTierOne(); ?>

</select>

<span id="wait_1" style="display: none;">
<img alt="Please Wait" src="ajax-loader.gif"/>
</span>
<span id="result_1" style="display: none;"></span>

</form>
</p>
<p>
<?php if(isset($_POST['submit'])){
      $drop = $_POST['drop_1'];
      $tier_two = $_POST['tier_two'];
      echo "You selected ";
      echo $drop." & ".$tier_two;
}
?>
<p><a href="three-tier/">View 3 Tier Select Box Example</a></p>
</body>
</html>
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Is there an elegant way. I did never implement own DB Queries into Joomla.
The DB-Part is a new table in Joomlas Main DB.
1. How is the connection to the table done?
2. Is there an other issue with the DB?
3. Where must the PHP-Code be implemented?
Regards
Roland
index.php
func.php
db.php