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