WITH A AS(
SELECT CASE WHEN (MOD(COUNT(*),2))=0 THEN COUNT(*)/2 ELSE ROUND(cast(COUNT(*) AS REAL)/2,0) END A
,CASE WHEN (MOD(COUNT(*),2) )=0 THEN COUNT(*)/2 +1 ELSE ROUND(cast(COUNT(*) AS REAL)/2,0) END B
FROM CONVENIENCE 
WHERE SURVEY_YEAR ='2019' AND KIND_CODE ='100'
)

SELECT ROUND(SUM(T_VALUE)/2 ,0) AS SA_MEDIAN 
FROM (
 SELECT cast(TOTAL_VALUE AS REAL) T_VALUE,row_number() over (order by TOTAL_VALUE ) as 順位
 FROM CONVENIENCE
 WHERE SURVEY_YEAR ='2019' AND KIND_CODE ='100'
) A
WHERE 順位 = (SELECT A FROM A)
OR 順位 = (SELECT B FROM A)