SELECT i.PORT_CODE '港コード'
    ,PORT_NAME '港名'
    ,SUM(CASE WHEN KIND_CODE = '110' THEN AMT END) '入国者数'
    ,SUM(CASE WHEN KIND_CODE = '120' THEN AMT END)'出国者数'
    ,(SUM(CASE WHEN KIND_CODE = '110' THEN AMT END)) - (SUM(CASE WHEN KIND_CODE = '120' THEN AMT END)) AS '差分'
FROM IMMIGRATION i JOIN PORT p ON i.PORT_CODE = p.PORT_CODE
    JOIN GRP  g ON i.GROUP_CODE = g.GROUP_CODE
GROUP BY i.PORT_CODE
ORDER BY 差分  DESC,i.PORT_CODE DESC;