SELECT
i.item_code AS CODE,
CASE 
WHEN ih.item_name IS NULL THEN i.item_name
WHEN i.item_name!=ih.item_name THEN  i.item_name 
ELSE NULL END AS NAME
FROM (
    SELECT
        item_code,
        item_name
    FROM ITEM
) i
LEFT JOIN (
    SELECT 
        item_code,
        item_name
    FROM ITEM_HISTORY
) ih
USING (item_code)
ORDER BY i.item_code DESC