SELECT
  AVG(TOTAL_VALUE)
FROM
  (
    SELECT
      TOTAL_VALUE
    FROM
      CONVENIENCE
    WHERE
      SURVEY_YEAR = '2019'
      AND KIND_CODE = '100'
    ORDER BY TOTAL_VALUE
    LIMIT 2 - (SELECT COUNT(*) FROM CONVENIENCE) % 2
    OFFSET (SELECT (COUNT(*) - 1) / 2 FROM CONVENIENCE)
  );