$db->loadObjectList and mysql_fetch_array error

i am working on a joomla module and i write this code for db connection and then fetch data from db and print it in a table

 $db = JFactory::getDBO();
 $query = $db->getQuery(true);

 if($q == ""){

 $query
  ->select(array('Stune_code,Stune_name,Stune_artist'))
  ->from('my_table')
  ->where('sub_cat_id = "4"')
  ->limit('$start, $per_page');

$query_pag_data = $db->loadObjectList();

$msg = "<table class='show-rslt'><tr>
<th class='tbl-header'>Song Title</th>
<th class='tbl-header'>Artist</th>
<th class='tbl-header'>Code</th>
</tr>";
while ($row = mysql_fetch_array($query_pag_data)) {

$msg .= "<tr>";
$msg .= "<td class='title'>" . htmlentities($row['Stune_name']) . "</td>";
$msg .= "<td class='title'>" . htmlentities($row['Stune_artist']) . "</td>";
$msg .= "<td class='title'>" . htmlentities($row['Stune_code']) . "</td>";
$msg .= "</tr>";
}
$msg .= "</table>";
$msg = "<div class='data'><ul>" . $msg . "</ul></div>"; // Content for Data

but it gives me this warning " Warning: mysql_fetch_array() expects parameter 1 to be resource, array given in C:"

then i debug it and use print_r() it gives me result like

Array 
(
[0] => stdClass Object
    (
        [Stune_code] => 501348
        [Stune_name] => xxx
        [Stune_artist] => abc
    )

[1] => stdClass Object
    (
        [Stune_code] => 501351
        [Stune_name] => xxx
        [Stune_artist] => abc
    )

[2] => stdClass Object
    (
        [Stune_code] => 5011727
        [Stune_name] => xxx
        [Stune_artist] => asd
    )
...
...

where am i wrong and what should i do to get the proper result

You've already loaded the data via the Joomla database object, so there is no need to try to fetch again. Just do a foreach to loop over the array.

First change your call to loadAssocList() (needed because you're trying to access the data using an associative array instead of object):

$query_pag_data = $db->loadAssocList();

Then change the loop to:

foreach($query_pag_data as $row) {
    $msg .= "<tr>";
    $msg .= "<td class='title'>" . htmlentities($row['Stune_name']) . "</td>";
    $msg .= "<td class='title'>" . htmlentities($row['Stune_artist']) . "</td>";
    $msg .= "<td class='title'>" . htmlentities($row['Stune_code']) . "</td>";
    $msg .= "</tr>";
}

The Joomla database object should be used for all database work, don't try to use any of the mysql_* functions.