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