SELECT 
    PORT_CODE AS 港コード,
    PORT_NAME AS 港名,
    SUM(CASE KIND_CODE WHEN 110 THEN AMT END) AS 入国者数,
    SUM(CASE KIND_CODE WHEN 120 THEN AMT END) AS 出国者数,
    SUM(CASE KIND_CODE WHEN 110 THEN AMT WHEN 120 THEN -AMT END) AS 差分
FROM IMMIGRATION JOIN PORT USING (PORT_CODE)
WHERE GROUP_CODE = 120
GROUP BY PORT_CODE HAVING 差分 > 0
ORDER BY 5 DESC, 1 DESC;