SELECT n.PORT_CODE AS '港コード', PORT_NAME AS '港名', inamt AS '入国者数', outamt AS '出国者数', inamt - outamt AS '差分'
FROM (SELECT PORT_CODE, KIND_CODE, AMT AS inamt
      FROM IMMIGRATION
      WHERE KIND_CODE = '110') AS n
         JOIN (SELECT PORT_CODE, KIND_CODE, AMT AS outamt
               FROM IMMIGRATION
               WHERE KIND_CODE = '120') AS s
              ON n.PORT_CODE = s.PORT_CODE
         JOIN PORT ON n.PORT_CODE = PORT.PORT_CODE
WHERE inamt > outamt
ORDER BY inamt - outamt DESC, n.PORT_CODE