SELECT ROUND(AVG(TOTAL_VALUE)) AS SA_MEDIAN
FROM (
    SELECT TOTAL_VALUE
    FROM (
        SELECT TOTAL_VALUE, 
               ROW_NUMBER() OVER (ORDER BY TOTAL_VALUE) as row, 
               COUNT(*) OVER () as total_rows
        FROM CONVENIENCE
        WHERE SURVEY_YEAR = '2019'
          AND KIND_CODE = '100'
    ) sub    
WHERE row in ((total_rows + 1) / 2, (total_rows + 2) / 2)
);