SELECT ROUND(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
                     WHERE SURVEY_YEAR = '2019'
                       AND KIND_CODE = '100') % 2
        OFFSET (SELECT (COUNT(*) - 1) / 2
                  FROM CONVENIENCE
                 WHERE SURVEY_YEAR = '2019'
                   AND KIND_CODE = '100'))
;