WITH avg_stdcost as(
    SELECT round(AVG(STD_COST_PRICE),1) as avgcost
    FROM SKU
    GROUP BY GOODS_CODE
),
hikui as(
    SELECT DISTINCT SKU_CODE as hikuicd,GD.STD_COST_PRICE AS hj
    FROM SKU,avg_stdcost,GOODS GD
    WHERE SKU.STD_COST_PRICE < avgcost
    AND SKU.GOODS_CODE = GD.GOODS_CODE
)

UPDATE SKU
SET STD_COST_PRICE = h.hj
FROM (SELECT hj,hikuicd FROM hikui) as h
WHERE SKU_CODE = h.hikuicd;