select DISTRICT_NAME
, sum(TOTAL_AMT) 
, sum(MALE_AMT)
, sum(FEMALE_AMT)
from(
select case when DISTRICT_NAME is null or DISTRICT_NAME = '' then '不明' else DISTRICT_NAME end DISTRICT_NAME
, TOTAL_AMT
, MALE_AMT 
, FEMALE_AMT 
from POPULATION
)
group by DISTRICT_NAME