update SKU set STD_COST_PRICE=AVG2
where SKU_CODE in (
  select s.SKU_CODE,g.AVG as AVG2
    from SKU s 
    left outer join (
      select
        GOODS_CODE, 
        round(avg(STD_COST_PRICE),1) as AVG
      from GOODS
      where GOODS_CODE in (select GOODS_CODE from SKU)
      group by GOODS_CODE) g
    on s.GOODS_CODE = g.GOODS_CODE
    where s.STD_COST_PRICE < g.AVG;