WITH TARGET AS (
SELECT
  *
FROM CONVENIENCE AS C
WHERE
  SURVEY_YEAR = '2019'
  AND
  KIND_CODE = '100'
ORDER BY TOTAL_VALUE DESC
)
, MID AS (
  SELECT TOTAL_VALUE
      FROM TARGET AS T
      ORDER BY TOTAL_VALUE DESC
      LIMIT 2 - (SELECT COUNT(*) FROM TARGET) % 2    -- odd 1, even 2
      OFFSET (SELECT (COUNT(*) - 1) / 2
              FROM TARGET)
)

SELECT
  -- *
  AVG(TOTAL_VALUE) AS SA_MEDIAN
FROM MID
-- FROM TARGET
;