select 
    item.item_code as CODE,
    case
        when item.item_name<>item_history.item_name then
            item.item_name
        when item.item_name=item_history.item_name then
            null
        when item_history.item_code is null then
            item.item_name
    end as NAME
from item
left outer join item_history
on item.item_code=item_history.item_code
order by code desc;