SELECT
    p.PORT_CODE as 港コード,
    p.PORT_NAME as 港名,
    sum(case when i.KIND_CODE = "110" then AMT else 0 end) as "入国者数",
    sum(case when i.KIND_CODE = "120" then AMT else 0 end) as "出国者数",
    sum(case when i.KIND_CODE = "110" then AMT else 0 end) - sum(case when i.KIND_CODE = "120" then AMT else 0 end) as "差分"
FROM
    PORT as p
JOIN
    IMMIGRATION as i on p.PORT_CODE = i.PORT_CODE
JOIN
    GRP as g on i.GROUP_CODE = g.GROUP_CODE
    
WHERE
    g.GROUP_NAME = "外国人"
    
GROUP BY
    港コード

having
    入国者数 > 出国者数

order by
    差分 DESC,
    港コード DESC