select 
ROUND(AVG(aaaa))	as SA_MEDIAN from 
(select IFNULL(TOTAL_VALUE,0) aaaa
,ROW_NUMBER() OVER (
                ORDER BY
                    TOTAL_VALUE
            ) AS ROWNUM
from CONVENIENCE where SURVEY_YEAR = 2019 and KIND_CODE = '100' 
) work
,(select count(1)/2 as hfCnt
from CONVENIENCE where SURVEY_YEAR = 2019 and KIND_CODE = '100' 
) work2
where work.ROWNUM >= work2.hfCnt
and  work.ROWNUM <= work2.hfCnt+1
;