WITH A AS (
SELECT ITEM_HISTORY.ITEM_CODE AS CODE, ITEM_HISTORY.ITEM_NAME AS NAME, ITEM_HISTORY.USER_UPDATE_DATETIME AS OLD, ITEM.USER_UPDATE_DATETIME AS NEW
FROM ITEM_HISTORY
LEFT JOIN ITEM
ON ITEM.ITEM_CODE = ITEM_HISTORY.ITEM_CODE
)

SELECT CODE, NAME, 
CASE 
WHEN OLD IS NULL THEN 'ADDED'
WHEN NEW IS NULL THEN 'DELETED'
WHEN OLD <> NEW THEN 'UPDATED'
END
AS COMP_RSLT
FROM
(
SELECT * FROM
 A
UNION 
SELECT ITEM_CODE AS CODE, ITEM_NAME AS NAME, NULL AS OLD, USER_UPDATE_DATETIME AS NEW
FROM ITEM
WHERE CODE NOT IN (SELECT CODE FROM A)
)
WHERE OLD IS NULL
OR NEW IS NULL
OR OLD <> NEW
ORDER BY CODE DESC