select 
 case count(*) % 2
  when 0 then sum(TOTAL_VALUE) / 2
  when 1 then sum(TOTAL_VALUE)
 end as SA_MEDIAN
from (
select *
from CONVENIENCE
where SURVEY_YEAR = '2019'
and KIND_CODE = '100'
order by TOTAL_VALUE
LIMIT 2
OFFSET (select 
    count(*) / 2
from CONVENIENCE
where SURVEY_YEAR = '2019'
and KIND_CODE = '100')
)