SELECT
 IMIN.PORT_CODE AS 港コード, 
 PT.PORT_NAME AS 港名, 
 IMIN.AMT AS 入国者数, 
 IMOUT.AMT AS 出国者数, 
 (IMIN.AMT - IMOUT.AMT) AS 差分 
 
FROM
 IMMIGRATION AS IMIN 
 
--結合(入国者) (出国者)
INNER JOIN IMMIGRATION AS IMOUT 
ON IMOUT.PORT_CODE = IMIN.PORT_CODE 
--'120'(出国者)
AND IMOUT.KIND_CODE = '120' 

INNER JOIN PORT AS PT 
ON PT.PORT_CODE = IMIN.PORT_CODE 

--GROUP_CODE = '120'外国人
--KIND_CODE'110'(入国者) 、'120'(出国者)
WHERE
    IMIN.GROUP_CODE = '120' 
    AND IMIN.KIND_CODE = '110' 
--外国人の入国者が出国者より多い港を抽出
    AND 差分 > 0 
    
    
--差分の降順 港コードの降順   
ORDER BY
    差分 DESC
    , IMIN.PORT_CODE DESC;