with tmp_1 AS(
select
    t1.item_code as CODE
    ,case
        when t2.item_code is null then t1.ITEM_NAME
        else 'NULL'
    end as NAME
from ITEM t1
left outer join ITEM_HISTORY t2
    on t1.item_code = t2.item_code
order by t1.item_code desc
),tmp_2 AS(
select
    t1.item_code as CODE
    ,case
        when t2.item_code is null then t1.ITEM_NAME
        else 'NULL'
    end as NAME
from ITEM_HISTORY t1
left outer join ITEM t2
    on t1.item_code = t2.item_code
order by t1.item_code desc
)
select
    *
from tmp_1
union
select
    *
from tmp_2
order by CODE desc