SELECT
P.PORT_CODE AS "港コード",
PORT_NAME AS "港名",
IM_IN.AMT "入国者数", 
IM_OUT.AMT AS "出国者数",
(IM_IN.AMT) - (IM_OUT.AMT)  AS "差分"
FROM
PORT AS P
INNER JOIN IMMIGRATION AS IM_IN ON P.PORT_CODE = IM_IN.PORT_CODE AND IM_IN.KIND_CODE = 110 
INNER JOIN IMMIGRATION AS IM_OUT ON P.PORT_CODE = IM_OUT.PORT_CODE AND IM_OUT.KIND_CODE = 120 
INNER JOIN GRP AS G ON G.GROUP_CODE = IM_IN.GROUP_CODE
INNER JOIN GRP AS G2 ON G2.GROUP_CODE = IM_OUT.GROUP_CODE
WHERE G.GROUP_CODE = 120 AND G2.GROUP_CODE = 120 AND "入国者数" > "出国者数"
GROUP BY P.PORT_CODE
ORDER BY "差分" DESC, "港コード" DESC;