SELECT 
    港コード,
    港名,
    入国者数,
    出国者数,
    入国者数 - 出国者数 AS 差分    
FROM 
    (SELECT 
        A.PORT_CODE AS 港コード,
        B.PORT_NAME AS 港名,
        SUM(CASE WHEN KIND_CODE = '110' THEN AMT ELSE 0 END) AS 入国者数,
        SUM(CASE WHEN KIND_CODE = '120' THEN AMT ELSE 0 END) AS 出国者数
    FROM IMMIGRATION AS A,PORT AS B
    WHERE A.PORT_CODE = B.PORT_CODE
    AND KIND_CODE IN('110','120')
    GROUP BY A.PORT_CODE
    HAVING 入国者数 > 出国者数)
ORDER BY 差分 DESC,港コード DESC