SELECT
    ALL_ITEM.ITEM_CODE AS CODE,
    ALL_ITEM.ITEM_NAME AS NAME,
    CASE
        WHEN ITEM.ITEM_CODE IS NULL THEN 'DELETED'
        WHEN ITEM_HISTORY.ITEM_CODE IS NULL THEN 'ADDED'
        WHEN ITEM.USER_UPDATE_DATETIME != ITEM_HISTORY.USER_UPDATE_DATETIME THEN 'UPDATE'
        ELSE NULL
    END AS COMP_RSLT
FROM
(
    SELECT
        ITEM_CODE,
        ITEM_NAME
    FROM
        ITEM
    UNION
    SELECT
        ITEM_CODE,
        ITEM_NAME
    FROM
        ITEM_HISTORY
) AS ALL_ITEM
LEFT JOIN
    ITEM
ON  ALL_ITEM.ITEM_CODE = ITEM.ITEM_CODE
LEFT JOIN
    ITEM_HISTORY
ON  ALL_ITEM.ITEM_CODE = ITEM_HISTORY.ITEM_CODE
WHERE
    COMP_RSLT IS NOT NULL
ORDER BY
    CODE DESC