-- SELECT SURVEY_YEAR, PF_CODE, KIND_CODE, TOTAL_VALUE
-- FROM CONVENIENCE c
-- WHERE c.SURVEY_YEAR = 2019 
--   AND c.KIND_CODE = 100
-- ORDER BY TOTAL_VALUE
SELECT ROUND(AVG(a.TOTAL_VALUE))
FROM 
    (SELECT *,
      ROW_NUMBER() OVER (ORDER BY c.TOTAL_VALUE) AS ROWNUM,
      COUNT(1) OVER() as TOTAL
    FROM
      CONVENIENCE c
    WHERE c.SURVEY_YEAR = 2019 
      AND c.KIND_CODE = 100) a
WHERE a.ROWNUM BETWEEN a.TOTAL * 1.0 / 2 AND a.TOTAL * 1.0 / 2 + 1
-- WORK.ROWNUM BETWEEN WORK.TOTAL_SUBJECT * 1.0 / 2 AND WORK.TOTAL_SUBJECT * 1.0 / 2 + 1