WITH 
OUT_POP as (
    SELECT
        PORT_CODE,
        PORT_NAME,
        GROUP_NAME,
        AMT as out_amt
    FROM IMMIGRATION
    JOIN PORT USING(PORT_CODE)
    JOIN GRP USING(GROUP_CODE)
    WHERE KIND_CODE = 120
),
IN_POP as (
    SELECT
        PORT_CODE,
        PORT_NAME,
        GROUP_NAME,
        AMT as in_amt
    FROM IMMIGRATION
    JOIN PORT USING(PORT_CODE)
    JOIN GRP USING(GROUP_CODE)
    WHERE KIND_CODE = 110
)
SELECT 
PORT_CODE as '港コード',
PORT_NAME as '港名',
in_amt as '入国者数',
out_amt as '出国者数',
in_amt - out_amt as '差分'
FROM IN_POP JOIN OUT_POP USING(PORT_CODE,PORT_NAME, GROUP_NAME)
WHERE GROUP_NAME = '外国人' AND in_amt - out_amt > 0
ORDER BY 差分 DESC, 港コード DESC