SELECT
    AVG(WORK.TOTAL_VALUE) AS SA_MEDIAN
FROM
    (
        SELECT
            *,
            ROW_NUMBER() OVER (
                PARTITION BY SURVEY_YEAR
                ORDER BY
                    TOTAL_VALUE
            ) AS ROWNUM,
            COUNT(1) OVER(PARTITION BY SURVEY_YEAR) AS TOTAL_SUBJECT
        FROM
            CONVENIENCE
        where 
            SURVEY_YEAR = 2019
    ) WORK
WHERE
    WORK.ROWNUM BETWEEN WORK.TOTAL_SUBJECT * 1.0 / 2
    AND WORK.TOTAL_SUBJECT * 1.0 / 2 + 1