SELECT 
PORT.PORT_CODE AS '港コード'
,PORT.PORT_NAME AS '港名'
,WK110.AMT110 AS '入国者数'
,WK120.AMT120 AS '出国者数'
,WK110.AMT110 - WK120.AMT120 AS '差分'
FROM (
 SELECT
  PORT_CODE,
  GROUP_CODE,
  SUM(AMT) AS AMT110
 FROM IMMIGRATION
 WHERE GROUP_CODE='120'
 AND KIND_CODE='110'
 GROUP BY PORT_CODE,GROUP_CODE) WK110
INNER JOIN (
 SELECT
  PORT_CODE,
  GROUP_CODE,
  SUM(AMT) AS AMT120
 FROM IMMIGRATION
 WHERE GROUP_CODE='120'
 AND KIND_CODE='120'
 GROUP BY PORT_CODE,GROUP_CODE) WK120
ON WK110.PORT_CODE=WK120.PORT_CODE
AND WK110.GROUP_CODE=WK120.GROUP_CODE
INNER JOIN PORT
ON PORT.PORT_CODE=WK110.PORT_CODE
WHERE WK110.AMT110 - WK120.AMT120 > 0
ORDER BY (WK110.AMT110 - WK120.AMT120) DESC, PORT.PORT_CODE DESC;