SELECT
PORT.PORT_CODE AS 港コード,
PORT.PORT_NAME AS 港名,
A.AMT AS 入国者数,
B.AMT AS 出国者数,
A.AMT-B.AMT AS 差分
FROM PORT
INNER JOIN
(SELECT
PORT.PORT_CODE,
IMM.AMT 
FROM IMMIGRATION AS IMM
INNER JOIN GRP
ON GRP.GROUP_CODE = IMM.GROUP_CODE
INNER JOIN PORT
ON PORT.PORT_CODE = IMM.PORT_CODE
WHERE IMM.GROUP_CODE = '120' AND IMM.KIND_CODE = '110') AS A
ON PORT.PORT_CODE = A.PORT_CODE
INNER JOIN
(SELECT
PORT.PORT_CODE,
IMM.AMT 
FROM IMMIGRATION AS IMM
INNER JOIN GRP
ON GRP.GROUP_CODE = IMM.GROUP_CODE
INNER JOIN PORT
ON PORT.PORT_CODE = IMM.PORT_CODE
WHERE IMM.GROUP_CODE = '120'AND IMM.KIND_CODE = '120') AS B
ON PORT.PORT_CODE = B.PORT_CODE
WHERE A.AMT-B.AMT > 0
order by A.AMT-B.AMT desc ,PORT.PORT_CODE desc