题解 | 获取指定客户每月的消费额
select
time,sum(if(t_type = 1,t_amount,0)) as total
from(
select substring_index(t_time,"-",2) as time, t_type , t_amount,c_name
from(
select *
from trade t
inner join customer c on t.t_cus =c.c_id
) a
where year(t_time) = 2023
) b
where c_name = 'Tom'
group by time
order by time
好多次我都怀疑自己，学文真的这么“没用”吗？后来发现其实文科人沟通力很强，工作中理解力也高，我看谁再说“文科无用”！