SELECT
  i.PORT_CODE AS `港コード`,
  PORT_NAME AS `港名`,
  innum AS `入国者数`,
  outnum AS `出国者数`,
  innum - outnum AS `差分`
FROM
  (
    SELECT
      PORT_CODE,
      SUM(CASE WHEN KIND_CODE = 110 THEN AMT ELSE 0 END) AS innum,
      SUM(CASE WHEN KIND_CODE = 120 THEN AMT ELSE 0 END) AS outnum
    FROM
      IMMIGRATION AS i
      LEFT JOIN GRP AS g ON i.GROUP_CODE = g.GROUP_CODE
    WHERE
      GROUP_NAME = "外国人"
    GROUP BY
      PORT_CODE
  ) AS i
  LEFT JOIN PORT AS p ON p.PORT_CODE = i.PORT_CODE
WHERE
  innum > outnum
ORDER BY
  `差分` desc,
  `港コード` desc