SELECT
      ITEM.ITEM_CODE AS CODE
    , ITEM.ITEM_NAME AS NAME
--    ,ITEM.USER_UPDATE_DATETIME as it,
--    ITEM_HISTORY.USER_UPDATE_DATETIME as it_h
    , CASE
        WHEN ITEM.USER_UPDATE_DATETIME is null THEN 'ADDED'
        WHEN ITEM_HISTORY.USER_UPDATE_DATETIME is null  THEN 'DELETED'
        ELSE 'UPDATED'
        END AS COMP_RSLT
FROM
    ITEM
    LEFT JOIN ITEM_HISTORY ON ITEM_HISTORY.ITEM_CODE = ITEM.ITEM_CODE
WHERE
--    NOT ITEM.USER_UPDATE_DATETIME = ITEM_HISTORY.USER_UPDATE_DATETIME

    ITEM.USER_UPDATE_DATETIME <> ITEM_HISTORY.USER_UPDATE_DATETIME
    or    ITEM.USER_UPDATE_DATETIME is null
    or
    ITEM_HISTORY.USER_UPDATE_DATETIME is null
ORDER BY
        CODE deSC
;