SELECT
  X.PORT_CODE AS "港コード"
, X.PORT_NAME AS "港名"
, X.NUM_ENTER AS "入国者数"
, X.NUM_EXIT  AS "出国者数"
, X.NUM_ENTER - X.NUM_EXIT AS "差分"
FROM (
  SELECT
    A.PORT_CODE AS PORT_CODE
  , B.PORT_NAME AS PORT_NAME
  , SUM(CASE WHEN A.KIND_CODE = '110' THEN AMT ELSE 0 END) AS NUM_ENTER
  , SUM(CASE WHEN A.KIND_CODE = '120' THEN AMT ELSE 0 END) AS NUM_EXIT
  FROM
    IMMIGRATION A
    INNER JOIN PORT B ON A.PORT_CODE  = B.PORT_CODE
    INNER JOIN GRP  C ON A.GROUP_CODE = C.GROUP_CODE
  WHERE
    C.GROUP_NAME = '外国人'
  GROUP BY
    A.PORT_CODE
  , B.PORT_NAME
) X
WHERE
  X.NUM_ENTER - X.NUM_EXIT > 0
ORDER BY
  X.NUM_ENTER - X.NUM_EXIT DESC
, X.PORT_CODE DESC
;