-- 商品テーブル（ITEM）と商品履歴テーブル（ITEM_HISTORY）を比較して表示するクエリ
SELECT 
    item.ITEM_CODE AS CODE,
    CASE 
        WHEN item.ITEM_NAME != item_history.ITEM_NAME THEN item.ITEM_NAME
        ELSE NULL
    END AS NAME
FROM ITEM item
LEFT JOIN ITEM_HISTORY item_history
ON item.ITEM_CODE = item_history.ITEM_CODE
ORDER BY item.ITEM_CODE;