select
    imm.PORT_CODE as '港コード'
    ,PORT.PORT_NAME as '港名'
    ,imm.AMT as '入国者数'
    ,immout.AMT as '出国者数'
    ,imm.AMT - immout.AMT as '差分'
from
    PORT
    inner join IMMIGRATION as imm -- 入国
        on imm.PORT_CODE = PORT.PORT_CODE
            and imm.GROUP_CODE = 120
            and imm.KIND_CODE = 110
    inner join IMMIGRATION as immout --出国
        on  PORT.PORT_CODE = immout.PORT_CODE
            and immout.GROUP_CODE = 120
            and immout.KIND_CODE = 120
where
    差分 > 0
order by
    差分 desc,港コード DESC;