update SKU as a
   set UPDATE_USER_NAME = 'MODIFY',
       USER_UPDATE_DATETIME = '2024-08-31 00:00:00',
       STD_COST_PRICE = (select c.STD_COST_PRICE
                           from GOODS c
                          where c.GOODS_CODE = a.GOODS_CODE)
  from (select GOODS_CODE,round(avg(STD_COST_PRICE)) as avgval
          from SKU
        group by GOODS_CODE) as b
 where a.GOODS_CODE = b.GOODS_CODE
   and a.STD_COST_PRICE < b.avgval