SELECT
  PRT.PORT_CODE AS '港コード',
  PRT.PORT_NAME AS '港名',
  N_IN AS '入国者数',
  N_OUT AS '出国者数',
  N_IN - N_OUT AS '差分'
FROM PORT AS PRT
JOIN (
  SELECT
      PORT_CODE,
      SUM(AMT) AS 'N_IN'
  FROM IMMIGRATION
  WHERE KIND_CODE = 110 AND GROUP_CODE = 120
  GROUP BY PORT_CODE
) AS STATS_IN
ON PRT.PORT_CODE = STATS_IN.PORT_CODE
JOIN (
  SELECT
      PORT_CODE,
      SUM(AMT) AS 'N_OUT'
  FROM IMMIGRATION
  WHERE KIND_CODE = 120 AND GROUP_CODE = 120
  GROUP BY PORT_CODE
) AS STATS_OUT
ON PRT.PORT_CODE = STATS_OUT.PORT_CODE
WHERE N_IN > N_OUT
ORDER BY N_IN - N_OUT DESC, PRT.PORT_CODE ASC
;