with base_tbl as 
(
  select total_value 
  from convenience
  where survey_year = 2019
     and kind_code = '100'
)
select round(avg(total_value),0) as SA_MEDIAN
from 
  (SELECT total_value
   FROM base_tbl
   ORDER BY total_value
   LIMIT 2 - (SELECT COUNT(*) FROM base_tbl) % 2    -- odd 1, even 2
   OFFSET (SELECT (COUNT(*) - 1) / 2 FROM base_tbl))
;