WITH CTE_AVGPRICE AS (
	SELECT
	    SKU.GOODS_CODE
		, ROUND(AVG(SKU.STD_COST_PRICE)) AS AVG_PRICE
	    , GOODS.STD_COST_PRICE           AS UPD_PRICE
	FROM
		SKU INNER JOIN GOODS ON
			SKU.GOODS_CODE = GOODS.GOODS_CODE
	GROUP BY
		SKU.GOODS_CODE
)

UPDATE
    SKU
SET 
    STD_COST_PRICE = CTE_AVGPRICE.UPD_PRICE
FROM
	CTE_AVGPRICE
WHERE
	SKU.GOODS_CODE = CTE_AVGPRICE.GOODS_CODE
    AND SKU.STD_COST_PRICE < CTE_AVGPRICE.AVG_PRICE
;