Mysql Left Join 和 Sum 无法正确处理按月和年分组

Question

我想通过mysql上的月份和年份分组获得total_amount和received_amt的总和。 但我面临一个问题。 问题是第二个表列总和按月和年分组不正确。

当前查询

SELECT t1.order_date,sum(IFNULL(t1.received_amt, 0)) as SumOfNO,
sum(IFNULL(t2.total_amount, 0)) as SumOfSM,
SUM(IFNULL(t1.received_amt, 0)  + IFNULL(t2.total_amount, 0)) AS Total
FROM `new_order` t1
LEFT JOIN
 (  select t2.sell_date,t2.total_amount, sum(total_amount) as Amount
    from sell_master t2
    group by YEAR(t2.sell_date), MONTH(t2.sell_date) 
 ) t2
 ON format(t1.order_date,'yyyy-MM') = format(t2.sell_date,'yyyy-MM')
GROUP BY YEAR(t1.order_date), MONTH(t1.order_date)
ORDER BY t1.order_date DESC

示例:

第一个表:new_order

第二个表:sell_master

表结构:

new_order

+----------------------------------------+
|order_date(date) | received_amt(double) |
+----------------------------------------+
|2007-10-06       | 245                  |
|2007-10-06       | 310                  |                             
|2007-10-06       | 275                  |                             
|2007-10-06       | 300                  |
+----------------------------------------+

sell_master

+----------------------------------------+
|sell_date(date)  | total_amount(double) |
+----------------------------------------+
|2007-10-06       | 10                   |
+----------------------------------------+

当前结果

+---------------------------------------+
|order_date | SumOfNO | SumOfSM | Total |
+---------------------------------------+
|2007-10-06 | 1130    | 40      |1170   |
+---------------------------------------+

预期结果

+---------------------------------------+
|order_date | SumOfNO | SumOfSM | Total |
+---------------------------------------+
|2007-10-06 | 1130    | 10      |1140   |
+---------------------------------------+

Answer 1

您不应在主查询中使用SUM(t2.total_amount)。您已经在子查询中计算了总和，您应该使用它。发生的情况是，您将 t2.total_amount 乘以 new_order 中匹配的行数。

也无需在 SUM() 中使用 IFNULL()，因为 SUM() 会忽略 null 值(大多数聚合函数都会忽略空值) )。

子查询应选择日期的年份和月份，以便您可以加入这些目录，而不是使用date_format。

由于您是按月分组，因此您不应该选择 t1.order_date ——这只会从组中随机选择一个月中的某一天。您应该只以 YYYY-MM 格式显示月份。

SELECT 
    DATE_FORMAT(t1.order_date, '%Y-%m') AS month,
    sum(t1.received_amt) as SumOfNO,
    IFNULL(t2.Amount, 0) as SumOfSM,
    sum(t1.received_amt) + IFNULL(t2.Amount, 0) AS Total
FROM `new_order` t1
LEFT JOIN
 (  select YEAR(t2.sell_date) AS year, MONTH(t2.sell_date) AS month,  sum(total_amount) as Amount
    from sell_master t2
    group by year, month
 ) t2
 ON YEAR(t1.order_date) = t2.year AND MONTH(t1.order_date) = month
GROUP BY month
ORDER BY month DESC

DEMO