select avg(TOTAL_VALUE) as SA_MEDIAN
from (
    select TOTAL_VALUE
    from CONVENIENCE
    where SURVEY_YEAR = 2019
    order by TOTAL_VALUE
    limit 2 -(
        select count(*)
        from CONVENIENCE) % 2
    offset (
        select (count(*) - 1) / 2
        from CONVENIENCE
    )
)
;