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 DESC
      LIMIT 2 - (SELECT COUNT(*) FROM CONVENIENCE) % 2    -- odd 1, even 2
      OFFSET (SELECT (COUNT(*) - 1) / 2
              FROM CONVENIENCE))
;