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