SELECT
    I.PORT_CODE AS 港コード
    ,P.PORT_NAME AS 港名
    ,SUM(CASE WHEN I.KIND_CODE = '110' THEN I.AMT END) AS 入国者数
    ,SUM(CASE WHEN I.KIND_CODE = '120' THEN I.AMT END) AS 出国者数
    ,SUM(CASE WHEN I.KIND_CODE = '110' THEN I.AMT END)-SUM(CASE WHEN I.KIND_CODE = '120' THEN I.AMT END) AS 差分
FROM
    IMMIGRATION AS I
    INNER JOIN PORT AS P
        ON I.PORT_CODE = P.PORT_CODE
    INNER JOIN GRP AS G
        ON I.GROUP_CODE = G.GROUP_CODE
WHERE I.GROUP_CODE = '120'
GROUP BY I.PORT_CODE
HAVING 差分>0
ORDER BY 差分 DESC, I.PORT_CODE ASC