WITH AGG AS (
  SELECT
    TOTAL_VALUE
  FROM
    CONVENIENCE
  WHERE
    SURVEY_YEAR = 2019
    AND KIND_CODE = '100'
  ORDER BY
    TOTAL_VALUE
), NUMAGG AS (
  SELECT
    *,
    (
      SELECT
        COUNT(*)
      FROM
        AGG
      WHERE
        TOTAL_VALUE <= z.TOTAL_VALUE
    ) AS id
  FROM
    AGG AS z
)

SELECT
  AVG(TOTAL_VALUE) AS  SA_MEDIAN
FROM
  NUMAGG
WHERE
  ID IN (
    SELECT
      CASE WHEN MAX(id) % 2 == 0 THEN MAX(id) / 2 ELSE MAX(id) / 2 END
    FROM
      NUMAGG
  )
  OR ID IN (
    SELECT
      CASE WHEN MAX(id) % 2 == 0 THEN MAX(id) + 1 ELSE MAX(id) / 2 + 1 END
    FROM
      NUMAGG
  )