SELECT
    IMMIGRATION.PORT_CODE AS 港コード,
    PORT.PORT_NAME AS 港名,
    (SELECT IMMIGRATION.AMT FROM IMMIGRATION WHERE IMMIGRATION.GROUP_CODE = 120 AND IMMIGRATION.KIND_CODE = 110) AS 入国者数,
    (SELECT IMMIGRATION.AMT FROM IMMIGRATION WHERE IMMIGRATION.GROUP_CODE = 120 AND IMMIGRATION.KIND_CODE = 120) AS 出国者数,
    (入国者数 - 出国者数) AS 差分
FROM IMMIGRATION
INNER JOIN PORT ON PORT.PORT_CODE = IMMIGRATION.PORT_CODE
WHERE 差分 > 0
ORDER BY 差分 DESC, 港コード DESC;