SELECT 
    P.PORT_CODE AS 港コード,
    P.PORT_NAME AS 港名,
    I.AMT AS 入国者数,
    O.AMT AS 出国者数,
    I.AMT - O.AMT AS 差分
FROM IMMIGRATION I
INNER JOIN IMMIGRATION O ON I.PORT_CODE = O.PORT_CODE AND O.KIND_CODE = 120 AND O.GROUP_CODE = 120
INNER JOIN PORT P ON P.PORT_CODE = I.PORT_CODE
WHERE I.KIND_CODE = 110 AND I.GROUP_CODE = 120 AND I.AMT >= O.AMT
ORDER BY 差分 DESC, 港コード DESC