SELECT AVG(TOTAL_VALUE) as SA_MEDIAN
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))

;