WITH AvgPrices AS (
    SELECT GOODS_CODE, ROUND(AVG(STD_COST_PRICE)) AS AvgPrice
    FROM SKU
    GROUP BY GOODS_CODE
)
UPDATE SKU
SET STD_COST_PRICE = (
    SELECT G.STD_COST_PRICE
    FROM GOODS G
    WHERE G.GOODS_CODE = SKU.GOODS_CODE
)
WHERE SKU_CODE IN (
    SELECT S.SKU_CODE
    FROM SKU S
    JOIN AvgPrices AP ON S.GOODS_CODE = AP.GOODS_CODE
    WHERE S.STD_COST_PRICE < AP.AvgPrice
)