with t1 as (
 select
  TOTAL_VALUE,
  row_number() over (order by TOTAL_VALUE) as row_id,
  (select count(1) from CONVENIENCE where SURVEY_YEAR = '2019' and KIND_CODE = '100') as ct
  from CONVENIENCE
  where
 SURVEY_YEAR = '2019'
  and
 KIND_CODE = '100'
)
select
 case
  when count(*) % 2 = 0 then
   (select round(avg(TOTAL_VALUE)) as median from t1 where row_id between ct/2.0 and ct/2.0 + 1)
  else
   (select TOTAL_VALUE as median from t1 where row_id = round(ct/2.0))
  end as "SA_MEDIAN"
from t1
;