题解 | 获取指定客户每月的消费额

select
    t.time,
    sum(t.t_amount) total
from
    (
        select
            t_time,
            DATE_FORMAT (t_time, '%Y-%m') time,
            t_cus,
            t_type,
            t_amount
        from
            trade
    ) t
    join customer c on t.t_cus = c.c_id
where
    c.c_name = 'Tom'
    and year (t.t_time) = 2023
    and t.t_type = 1
group by
    t.time
order by t.time ;