SELECT
    N.prefecture,
    SUM(P.total_amount)
FROM (
    SELECT
        SUBSTR(DISTRICT_CODE, 1, 2) AS prefecture_code,
        TOTAL_AMT AS total_amount
    FROM
    POPULATION
) AS P
LEFT OUTER JOIN (
    SELECT
        SUBSTR(DISTRICT_CODE, 1, 2) AS prefecture_code,
        DISTRICT_NAME AS prefecture
    FROM
        POPULATION
    WHERE
        LVL = 2
) AS N
ON P.prefecture_code = N.prefecture_code
GROUP BY
    P.prefecture_code
HAVING
    N.prefecture IS NOT NULL
ORDER BY
    P.total_amount DESC;