select avg(TOTAL_VALUE) as SA_MEDIAN from
  (
    select PF_CODE, TOTAL_VALUE, row_number() over(order by TOTAL_VALUE) as num
    from CONVENIENCE
    where SURVEY_YEAR = 2019 and KIND_CODE = 100
  )
where
    case 
      (
         select count(1) % 2
         from CONVENIENCE
         where SURVEY_YEAR = 2019 and KIND_CODE = 100
      )
    when 0 then
      num in
      (
        (
          select count(1) / 2
          from CONVENIENCE
          where SURVEY_YEAR = 2019 and KIND_CODE = 100
        ),
        (
          select count(1) / 2 + 1
          from CONVENIENCE
          where SURVEY_YEAR = 2019 and KIND_CODE = 100
        )
      )
    when 1 then
      num =
      (
        select (count(1) + 1)/ 2
        from CONVENIENCE
        where SURVEY_YEAR = 2019 and KIND_CODE = 100
      )
    end
;