SELECT (MIN(TOTAL_VALUE) + (MAX(TOTAL_VALUE) - MIN(TOTAL_VALUE))/2) as SA_MEDIAN
FROM (
   SELECT TOTAL_VALUE
      FROM CONVENIENCE
      WHERE SURVEY_YEAR = 2019
      ORDER BY TOTAL_VALUE
      LIMIT 2 - ((SELECT COUNT(*) FROM CONVENIENCE) % 2) -- odd 1, even 2
      OFFSET (SELECT (COUNT(*) - 1) / 2 FROM CONVENIENCE)
);