UPDATE
    SKU
SET
    STD_COST_PRICE = (
        SELECT
            STD_COST_PRICE
        FROM
            GOODS
        WHERE
            GOODS.GOODS_CODE = SKU.GOODS_CODE
    )
FROM
    (
        WITH GOODS_AVG_COST(GOODS_CODE, AVG_COST) AS(
            SELECT
                GOODS_CODE, ROUND(AVG(STD_COST_PRICE)) AS AVG_COST
            FROM
                SKU
            GROUP BY
                GOODS_CODE
        )
        
        SELECT
            SKU.SKU_CODE
        FROM
            GOODS_AVG_COST, SKU
        WHERE
            GOODS_AVG_COST.GOODS_CODE = SKU.GOODS_CODE
            AND SKU.STD_COST_PRICE < GOODS_AVG_COST.AVG_COST
    ) AS UPD_TARGET
WHERE
    SKU.SKU_CODE = UPD_TARGET.SKU_CODE