-- 追加された商品を検出
SELECT
    I.ITEM_CODE AS CODE,
    I.ITEM_NAME AS NAME,
    'ADDED' AS COMP_RSLT
FROM ITEM I
LEFT JOIN ITEM_HISTORY IH ON I.ITEM_CODE = IH.ITEM_CODE
WHERE IH.ITEM_CODE IS NULL

UNION ALL

-- 更新された商品を検出
SELECT
    I.ITEM_CODE AS CODE,
    I.ITEM_NAME AS NAME,
    'UPDATED' AS COMP_RSLT
FROM ITEM I
INNER JOIN ITEM_HISTORY IH ON I.ITEM_CODE = IH.ITEM_CODE
WHERE I.USER_UPDATE_DATETIME != IH.USER_UPDATE_DATETIME

UNION ALL

-- 削除された商品を検出
SELECT
    IH.ITEM_CODE AS CODE,
    IH.ITEM_NAME AS NAME,
    'DELETED' AS COMP_RSLT
FROM ITEM_HISTORY IH
LEFT JOIN ITEM I ON IH.ITEM_CODE = I.ITEM_CODE
WHERE I.ITEM_CODE IS NULL

-- 結果のソート
ORDER BY CODE DESC;