SELECT
    a.PORT_CODE     港コード
    , b.PORT_NAME   港名
    , SUM(CASE WHEN GROUP_CODE = 120 AND KIND_CODE = 110 THEN a.AMT ELSE 0 END) 入国者数
    , SUM(CASE WHEN GROUP_CODE = 120 AND KIND_CODE = 120 THEN a.AMT ELSE 0 END) 出国者数
    , SUM(CASE WHEN GROUP_CODE = 120 AND KIND_CODE = 110 THEN a.AMT ELSE 0 END) - SUM(CASE WHEN GROUP_CODE = 120 AND KIND_CODE = 120 THEN a.AMT ELSE 0 END) 差分

FROM
    IMMIGRATION a
        LEFT JOIN PORT b
            ON a.PORT_CODE = b.PORT_CODE

GROUP BY
    a.PORT_CODE
    , b.PORT_NAME

HAVING
    入国者数 > 出国者数

ORDER BY
    差分 DESC
    , a.PORT_CODE DESC
;