SELECT
    ROUND(SUM(TOTAL_VALUE)/2,0) AS SA_MEDIAN
FROM(
    SELECT
    		PF_CODE
    		,TOTAL_VALUE
    		,rank
    FROM (
    	SELECT
    		PF_CODE
    		,TOTAL_VALUE
    		,RANK() OVER(ORDER BY TOTAL_VALUE DESC) AS rank
    	FROM CONVENIENCE
    	WHERE SURVEY_YEAR = 2019
    		AND KIND_CODE = '100'
    	)
    WHERE
        rank IN (18,19)
    )