select
    A.ITEM_CODE CODE,
    CASE 
        WHEN A.ITEM_NAME = B.ITEM_NAME THEN 'NULL'
        WHEN A.ITEM_NAME is not null THEN A.ITEM_NAME
        ELSE A.ITEM_NAME END NAME
from
    ITEM A
full join ITEM_HISTORY B
    on A.ITEM_CODE = B.ITEM_CODE
order by
    A.ITEM_CODE desc