WITH t AS (
    SELECT TOTAL_VALUE AS v FROM CONVENIENCE WHERE SURVEY_YEAR = 2019 AND KIND_CODE = '100'
)
, u AS (
    SELECT ROUND(COUNT(0) * 0.5) AS c FROM t
)

SELECT
    ROUND(
        ((SELECT MAX(v) FROM (SELECT v FROM t ORDER BY v ASC LIMIT (SELECT c FROM u)))
        + (SELECT MIN(v) FROM (SELECT v FROM t ORDER BY v DESC LIMIT (SELECT c FROM u))))
        * 0.5
    ) AS SA_MEDIAN
;