SELECT
    I1.PORT_CODE AS 港コード
    ,P.PORT_NAME AS 港名
    ,I1.入国者 AS 入国者数
    ,I2.出国者 AS 出国者数
    ,I1.入国者 - I2.出国者 AS 差分
FROM
    (SELECT PORT_CODE, AMT AS 入国者 FROM IMMIGRATION WHERE GROUP_CODE ='120' AND KIND_CODE = '110') I1
    INNER JOIN (SELECT PORT_CODE, AMT AS 出国者 FROM IMMIGRATION WHERE GROUP_CODE ='120' AND KIND_CODE = '120') I2 ON I1.PORT_CODE = I2.PORT_CODE
    INNER JOIN PORT P ON I1.PORT_CODE = P.PORT_CODE
WHERE
    I1.入国者 > I2.出国者
ORDER BY
    差分 DESC
    ,港コード DESC
;