Magento1 tax rate changing script (originally developed for Corona-caused tax rate change in Germany)

change_taxrate.php

<?php

require_once 'abstract.php';

class TaxrateChange extends Mage_Shell_Abstract
{
    public function run()
    {
        $this->validateInput();
        $this->changeTaxRate();
    }

    protected function changeTaxRate()
    {
        /** @var  $resource Mage_Core_Model_Resource $resource */
        $resource = Mage::getSingleton('core/resource');
        /** @var $connection Magento_Db_Adapter_Pdo_Mysql */
        $connection = $resource->getConnection('read_write');
        $tblTaxCalculationRate = $resource->getTableName('tax_calculation_rate');

        $query = implode("\n", [
            "UPDATE `{$tblTaxCalculationRate}`",
            "SET rate = :new_tax_rate",
            "WHERE rate = :current_tax_rate",
            "AND tax_country_id = :county_id",
        ]);

        $statement = $connection->prepare($query);
        $statement->bindValue('new_tax_rate', $this->getArgumentNewRate());
        $statement->bindValue('current_tax_rate', $this->getArgumentCurrentRate());
        $statement->bindValue('county_id', $this->getArgumentCountryId());
        $result = $statement->execute();

        if (true === $result && $statement->rowCount() == 1) {
            echo "Successfully changed tax rate\n";
        } else if (true === $result && $statement->rowCount() == 0) {
            echo "Query executed but no tax rate changed\n";
        } else {
            echo "Changing tax rate failed\n";
        }
    }

    protected function validateInput()
    {
        if (!$this->getArgumentCountryId()
            || !$this->getArgumentCountryId()
            || !$this->getArgumentNewRate()) {
            Mage::throwException('Missing arguments');
        }
    }

    protected function getArgumentCountryId()
    {
        return trim($this->getArg('country_id'));
    }

    protected function getArgumentCurrentRate()
    {
        return trim(
            $this->formatInputRate($this->getArg('current_rate'))
        );
    }

    protected function getArgumentNewRate()
    {
        return trim(
            $this->formatInputRate($this->getArg('new_rate'))
        );
    }

    protected function formatInputRate($inputRate)
    {
        return number_format(
            (float) $inputRate,
            4
        );
    }

    public function usageHelp()
    {
        return <<<USAGE
Usage:  php -f change_taxrate.php -- [options]
Example: php -f change_taxrate.php --country_id "DE" --current_rate "19" --new_rate "16"

  h                This help
  country_id        ISO-2 Country code
  current_rate      Current tax rate to change
  new_rate          Taxrate change to

USAGE;
    }
}

$shell = new TaxrateChange();
$shell->run();