--【問題３】データ操作履歴
SELECT
	COALESCE(A.ITEM_CODE,B.ITEM_CODE) AS CODE
,	COALESCE(A.ITEM_NAME,B.ITEM_NAME) AS NAME
,	CASE
		WHEN B.ITEM_CODE IS NULL THEN 'ADDED'
		WHEN A.USER_UPDATE_DATETIME <> B.USER_UPDATE_DATETIME THEN 'UPDATED'
		WHEN A.ITEM_CODE IS NULL THEN 'DELETED'
	END AS COMP_RSLT
FROM
	ITEM A
FULL OUTER JOIN
	ITEM_HISTORY B
ON
	A.ITEM_CODE = B.ITEM_CODE
WHERE
	A.ITEM_CODE IS NULL
OR	B.ITEM_CODE IS NULL
OR	A.USER_UPDATE_DATETIME <> B.USER_UPDATE_DATETIME
ORDER BY
	COALESCE(A.ITEM_CODE,B.ITEM_CODE) DESC