SELECT CODEa as CODE,
CASE
    WHEN NAMEb = NULL THEN NAMEa
    WHEN NAMEa != NAMEb THEN NAMEa
    WHEN NAMEa = NAMEb THEN NULL
END as NAME
FROM (
SELECT a.ITEM_CODE as CODEa, b.ITEM_CODE as CODEb, a.ITEM_NAME as NAMEa,b.ITEM_NAME as NAMEb
FROM ITEM a
LEFT JOIN ITEM_HISTORY b
ON a.ITEM_CODE = b.ITEM_CODE
) as a

ORDER BY CODE desc;