WITH AVG_PRICE AS (
    SELECT
        GOODS_CODE
        , ROUND(AVG(STD_COST_PRICE)) AS PRICE
    FROM
        SKU
    GROUP BY
        GOODS_CODE
)

UPDATE SKU
SET
    STD_COST_PRICE = GOODS.STD_COST_PRICE
FROM
    GOODS
    INNER JOIN AVG_PRICE USING(GOODS_CODE)
WHERE
    SKU.GOODS_CODE = GOODS.GOODS_CODE
    AND SKU.STD_COST_PRICE < AVG_PRICE.PRICE