题解 | 统计各等级会员用户下订单总额

select
    u.vip,
    ifnull(sum(o.order_price),0) as order_total
from
    uservip_tb u
    left join order_tb o on o.user_id=u.user_id
group by
    u.vip
order by
    order_total desc 

IFNULL(..., 0) 或 COALESCE(..., 0) : 若没有订单记录则求和为 NULL，转成 0