SELECT IG.PORT_CODE AS 港コード
       ,P.PORT_NAME AS 港名
       ,IG.nyu AS 入国者数
       ,IG.syu AS 出国者数
       ,IG.sabu AS 差分
FROM (SELECT PORT_CODE
             ,SUM(CASE WHEN KIND_CODE = "110" THEN AMT ELSE 0 END  ) AS nyu
             ,SUM(CASE WHEN KIND_CODE = "120" THEN AMT ELSE 0 END  ) AS syu
             ,SUM(CASE WHEN KIND_CODE = "110" THEN AMT ELSE 0 END  ) - SUM(CASE WHEN KIND_CODE = "120" THEN AMT ELSE 0 END  ) AS sabu
      FROM IMMIGRATION 
      WHERE GROUP_CODE = "120"
      GROUP BY PORT_CODE
      ORDER BY SUM(CASE WHEN KIND_CODE = "110" THEN AMT ELSE 0 END  ) - SUM(CASE WHEN KIND_CODE = "120" THEN AMT ELSE 0 END  ) DESC
         ,PORT_CODE DESC
      ) AS IG
INNER JOIN PORT AS P
ON IG.PORT_CODE = P.PORT_CODE
WHERE IG.sabu > 0