SELECT
    ROUND(AVG(TOTAL_VALUE)) AS SA_MEDIAN
FROM (
    SELECT
        ROW_NUMBER() OVER (ORDER BY TOTAL_VALUE ASC) AS ASC_RANK,
        ROW_NUMBER() OVER (ORDER BY TOTAL_VALUE DESC) AS DESC_RANK,
        TOTAL_VALUE
    FROM
        CONVENIENCE
    WHERE
        KIND_CODE = '100' AND
        SURVEY_YEAR = 2019
) AS RANK
WHERE
    ASC_RANK = DESC_RANK OR
    ASC_RANK = DESC_RANK + 1 OR
    ASC_RANK = DESC_RANK - 1