SELECT PT.PORT_CODE AS 港コード,
       PT.PORT_NAME AS 港名,
       IMG1.AMT AS 入国者数,
       IMG2.AMT AS 出国者数,
       IMG1.AMT- IMG2.AMT AS 差分
FROM IMMIGRATION AS IMG1
INNER JOIN IMMIGRATION AS IMG2 ON IMG1.PORT_CODE = IMG2.PORT_CODE
AND IMG2.KIND_CODE = 120 --出国者=120
AND IMG2.GROUP_CODE = 120 --外国人=120
INNER JOIN PORT AS PT ON IMG1.PORT_CODE = PT.PORT_CODE
WHERE IMG1.KIND_CODE = 110
AND IMG1.GROUP_CODE = 120
GROUP BY PT.PORT_CODE
HAVING IMG1.AMT- IMG2.AMT > 0
ORDER BY 差分 DESC ,PT.PORT_CODE DESC;