WITH tbl AS
(
SELECT 
    DISTRICT_CODE,
    CASE DISTRICT_NAME
            WHEN '' THEN '不明' 
            ELSE DISTRICT_NAME
        END AS DISTRICT_NAME,
    TOTAL_AMT,
    MALE_AMT,
    FEMALE_AMT
FROM
    POPULATION
)
SELECT
    DISTRICT_CODE,
    ifnull(DISTRICT_NAME, '不明') AS DISTRICT_NAME,
    TOTAL_AMT,
    MALE_AMT,
    FEMALE_AMT
FROM
    tbl
ORDER BY
    DISTRICT_CODE