Add column to exists table using upgrade script

<?php 
$installer = $this;
$installer->startSetup();
try {
	$table = $installer->getTable('awrma/entity');
	$conn = $installer->getConnection();
	$conn->addColumn($table, 'authorize_code', "varchar(100) default NULL AFTER `tracking_code`");
	$conn->commit();
} catch (Exception $ex) {
    Mage::logException($ex);
}

$installer->endSetup();