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

UPDATE 
    SKU
SET 
    SKU.STD_COST_PRICE = GOODS.STD_COST_PRICE
FROM 
    AVG
WHERE 
    GOODS.GOODS_CODE = AVG.GOODS_CODE
    AND GOODS.STD_COST_PRICE < AVG.AVG;
    
SELECT * FROM SKU