题解 | 获取指定客户每月的消费额

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