text: SELECT 
      `c`.`continent_code`,
      `c`.`currency_code`,
      COUNT(*) AS `currency_usage`
  FROM
      `countries` AS `c`
  GROUP BY `c`.`continent_code` , `c`.`currency_code`
  HAVING `currency_usage` > 1
      AND `currency_usage` = (SELECT 
          COUNT(*) AS `most_used_curr`
      FROM
          `countries` AS `c2`
      WHERE
          `c2`.`continent_code` = `c`.`continent_code`
      GROUP BY `c2`.`currency_code`
      ORDER BY `most_used_curr` DESC
      LIMIT 1)
  ORDER BY `c`.`continent_code` , `c`.`currency_code`;