select CODE, CASE WHEN HISTCODE is null THEN ITEMNAME WHEN ITEMNAME <> HISTNAME THEN ITEMNAME ELSE null END as NAME
FROM (select i.ITEM_CODE as CODE, h.ITEM_CODE as HISTCODE, i.ITEM_NAME as ITEMNAME, h.ITEM_NAME as HISTNAME 
   from ITEM i left outer join ITEM_HISTORY h on i.ITEM_CODE=h.ITEM_CODE
) difftbl
order by CODE desc
;