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