SELECT PT.PORT_CODE 港コード, PT.PORT_NAME 港名, IM110.AMT 入国者数, IM120.AMT 出国者数, (IM110.AMT - IM120.AMT) 差分 
FROM IMMIGRATION AS IM
    INNER JOIN PORT PT ON PT.PORT_CODE = IM.PORT_CODE 
    INNER JOIN IMMIGRATION IM110 ON IM.PORT_CODE = IM110.PORT_CODE 
        AND IM.GROUP_CODE = IM110.GROUP_CODE 
        AND IM110.KIND_CODE = 110
    INNER JOIN IMMIGRATION IM120 ON IM.PORT_CODE = IM120.PORT_CODE 
        AND IM.GROUP_CODE = IM120.GROUP_CODE 
        AND IM120.KIND_CODE = 120
WHERE IM.GROUP_CODE = 120 AND 差分 > 0 
GROUP BY 港コード, 港名, 入国者数, 出国者数
ORDER BY 差分 DESC, 港コード DESC;