<?php
define('WPSQT_VERSION', '1.2.1');
$oldVersion = get_option('wpsqt_version');
update_option('wpsqt_version',WPSQT_VERSION);

// Simple way of checking if an it's an update or not.
if ( !empty($oldVersion) && (version_compare($oldVersion, WPSQT_VERSION) < 0) ){
	// Do upgrade stuff.
}