题解 | 获取指定客户每月的消费额

SELECT DATE_FORMAT(re.time, "%Y-%m") as time, SUM(re.t_amount) AS total
FROM
    (
SELECT
t_time as time,
t_amount
FROM
trade
LEFT JOIN customer ON trade.t_cus = customer.c_id
WHERE
customer.c_name = "Tom"
AND YEAR (trade.t_time) = 2023
AND trade.t_type = 1
GROUP BY
t_amount,
t_time
    ) as re
GROUP BY DATE_FORMAT(re.time, "%Y-%m")
ORDER BY DATE_FORMAT(re.time, "%Y-%m")