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
        OFFSET 
            (SELECT (COUNT(*) - 1)/2 FROM CONVENIENCE)
    )