SELECT ROUND(AVG(TOTAL_VALUE)) AS  SA_MEDIAN
FROM (SELECT TOTAL_VALUE
      FROM CONVENIENCE
      WHERE SURVEY_YEAR = '2019'
        AND KIND_CODE = '100'
        AND TOTAL_VALUE <> 0
      ORDER BY TOTAL_VALUE DESC
      LIMIT 2
      OFFSET (SELECT (COUNT(*) - 1) / 2
              FROM CONVENIENCE))