with
    t1 as (
        select
            user_id,
            sales_num * goods_price sales
        from
            sales_tb s
            left join goods_tb g on s.goods_id = g.goods_id
    )
select
    round(sum(sales), 3) sales_total,
    round(sum(sales) / count(distinct user_id), 3) per_trans
from
    t1