with port_imm as(
    select 
        p.PORT_CODE as port_code, 
        p.PORT_NAME as port_name,
        sum(case when i.GROUP_CODE = 120 and i.KIND_CODE = 110 then i.AMT else 0 end) as import, 
        sum(case when i.GROUP_CODE = 120 and i.KIND_CODE = 120 then i.AMT else 0 end) as export 
    from IMMIGRATION as i
    inner join port as p
    on i.PORT_CODE = p.PORT_CODE
    group by i.PORT_CODE
)
select         
    PORT_CODE as '港コード', 
    PORT_NAME as '港名',
    import as '入国者数', 
    export as '出国者数', 
    import - export as '差分'
from port_imm
where import > export
order by 差分 desc, 港コード desc
;