ON DUPLICATE KEY UPDATE

global $wpdb;
// Inserts values into woocommerce_tax_rates
$wpdb->query("INSERT INTO wp_woocommerce_tax_rates (tax_rate_country, tax_rate_state, tax_rate, tax_rate_name) VALUES ('$country', '$state', '$rate', '$city')
ON DUPLICATE KEY UPDATE tax_rate_id='tax_rate_id'");

so I am trying to update zip code tax rates based on a csv file, so I assume I could use the column named tax_rate_id as that stores the actual zip code which would be unique. So I am trying to write the above statement so that if a row exist only update that row, if not insert it as a new row.