SELECT
  i.PORT_CODE AS 港コード,
  b.PORT_NAME AS 港名,
  SUM(CASE WHEN i.KIND_CODE = 110 THEN AMT ELSE 0 END) AS 入国者数,
  SUM(CASE WHEN i.KIND_CODE = 120 THEN AMT ELSE 0 END) AS 出国者数,
  SUM(CASE WHEN i.KIND_CODE = 110 THEN AMT ELSE 0 END) - SUM(CASE WHEN i.KIND_CODE = 120 THEN AMT ELSE 0 END) AS 差分
FROM
  IMMIGRATION AS i
  LEFT OUTER JOIN GRP AS a ON i.GROUP_CODE = a.GROUP_CODE
  LEFT OUTER JOIN PORT AS b ON i.PORT_CODE = b.PORT_CODE
WHERE
  i.GROUP_CODE = 120
GROUP BY
  i.PORT_CODE,
  i.GROUP_CODE
HAVING
  差分 > 0
ORDER BY
  差分 DESC,
  港コード DESC