SELECT IM1.PORT_CODE "港コード",POR.PORT_NAME "港名",IM1.AMT 
"入国者数",IM2.AMT "出国者数",(IM2.AMT-IM1.AMT) "差分"
FROM IMMIGRATION IM1 JOIN IMMIGRATION IM2 ON IM1.GROUP_CODE = IM2.GROUP_CODE
AND IM1.PORT_CODE = IM2.PORT_CODE
AND IM1.KIND_CODE = 120
JOIN PORT POR ON IM1.PORT_CODE = POR.PORT_CODE
WHERE IM1.GROUP_CODE = 120
AND (IM2.AMT-IM1.AMT)>0
ORDER BY IM2.AMT-IM1.AMT DESC
,IM1.PORT_CODE DESC;