题解 | #获取指定客户每月的消费额#

SELECT
    date_format (t_time, '%Y-%m') time,
    sum(t_amount) total
FROM
    trade t
    LEFT join customer c ON t.t_cus = c.c_id
WHERE
    c_name = 'Tom'
    AND YEAR (t_time) = '2023'
    AND t_type = 1
GROUP BY
    1
order by
    1

1. 关联表方便筛选Tom
2. where筛选限制
3. group by时间