题解 | 获取指定客户每月的消费额

select left(t_time,7) time,sum(t_amount) total
from trade t 
inner join customer c 
on c.c_id=t.t_cus and c_name ='Tom' and t_time like '2023%' and t_type=1
group by left(t_time,7)
order by time;

要注意消费金额，消费是1，细碎的条件不能漏了