WITH SortedValues AS (
  SELECT TOTAL_VALUE,
         ROW_NUMBER() OVER (ORDER BY TOTAL_VALUE) AS row_num_asc,
         ROW_NUMBER() OVER (ORDER BY TOTAL_VALUE DESC) AS row_num_desc
  FROM CONVENIENCE
  WHERE SURVEY_YEAR = 2019
    AND KIND_CODE = '100'
)
SELECT AVG(TOTAL_VALUE) AS MEDIAN_VALUE
FROM SortedValues
WHERE row_num_asc = row_num_desc;