UPDATE
  SKU
SET
  STD_COST_PRICE = (SELECT GOODS.STD_COST_PRICE FROM GOODS WHERE SKU.GOODS_CODE = GOODS.GOODS_CODE)
WHERE
  SKU_CODE IN (
    SELECT
      SKU_CODE
    FROM (
      SELECT
        SKU_CODE
      , STD_COST_PRICE
      , AVG(STD_COST_PRICE) OVER (PARTITION BY GOODS_CODE) AS AVG_STD_COST_PRICE
      FROM
        SKU
    ) X
    WHERE
      X.STD_COST_PRICE < X.AVG_STD_COST_PRICE
  )
;