SELECT
    ROUND(AVG(TOTAL_VALUE)) AS SA_MEDIAN
FROM(
SELECT
    *
    ,row_number() over(order by TOTAL_VALUE) AS NO
    , ( SELECT 
            COUNT(*) 
        FROM 
            CONVENIENCE 
        WHERE
            SURVEY_YEAR = '2019'
            AND KIND_CODE = '100') as CO
FROM
    CONVENIENCE
WHERE
    SURVEY_YEAR = '2019'
    AND KIND_CODE = '100'
ORDER BY
    TOTAL_VALUE
)
WHERE
    NO BETWEEN CO/2. and CO/2. + 1.