-- 調査年(SURVEY_YEAR)が2019年の販売額(TOTAL_VALUE)の中央値を求めなさい。
-- ただし、種別コード(KIND_CODE)が'100' (販売額)のデータを対象とする。また
select
    round(avg(TOTAL_VALUE)) as SA_MEDIAN
from
(
    select
        TOTAL_VALUE 
    from
        CONVENIENCE
    where
        SURVEY_YEAR = 2019
    and
        KIND_CODE = "100"
    order by
        TOTAL_VALUE 
    limit
        2-(select count(*) from CONVENIENCE where SURVEY_YEAR = 2019 and KIND_CODE = "100") % 2
    offset
        (select count(*)-1 from CONVENIENCE where SURVEY_YEAR = 2019 and KIND_CODE = "100") / 2
)