tp3.2 how to compare two fields

Use exp

if ($_GET['owe_property'] || $_GET['owe_property'] !== NULL) {
    if ((int)$_GET['owe_property'] === 1) {
        $where['generate_property_fee'] = ['exp','> prepay_property_fee'];
    } else {
        $where['generate_property_fee'] = ['exp','<= prepay_property_fee'];
    }
    $this->assign('owe_property', (int)$_GET['owe_property']);
}

very useful!