SELECT
       ROUND(
         AVG(
         CASE counter % 2
           WHEN 0 THEN CASE WHEN rn IN (counter / 2, counter / 2 + 1) THEN TOTAL_VALUE END 
           WHEN 1 THEN CASE WHEN rn = counter / 2 + 1 THEN TOTAL_VALUE END
         END
       )
       ,0) AS SA_MEDIAN
FROM (        
  SELECT *,
         ROW_NUMBER() OVER (PARTITION BY PF_CODE ORDER BY TOTAL_VALUE) rn,
         COUNT(*) OVER (PARTITION BY PF_CODE) counter
  FROM CONVENIENCE
)