加入两个表并使组和总和正确答案

【问题标题】：JOINing two tables and make group and sums correct加入两个表并使组和总和正确
【发布时间】：2016-10-30 00:24:27
【问题描述】：

数小时以来一直在尝试解决这个问题，非常感谢您的帮助！

所以我有两个表，transactions 和 transactions_rebuy

我的 SELECT 目标是加入/组合这些表并按日期分组。

现在我有这样的声明：

SELECT tr.SoldDate, SUM(tr.TotalAmount) as SumByReceipt,
COUNT(DISTINCT(tr.`ForsNr`)) as TotalCustomers, rebuy.RebuySum
FROM transactions tr   
CROSS JOIN (
SELECT SUM(TotalAmount) as RebuySum
    FROM transactions_rebuy
    WHERE SoldDate BETWEEN '2016-10-22' AND '2016-10-27'
    ) as rebuy
WHERE tr.SoldDate BETWEEN '2016-10-22' AND '2016-10-27' 
GROUP by tr.SoldDate
ORDER by tr.SoldDate DESC

这给了我以下结果：

SaldDatum SumByReceipt TotalCustomers RebuySum

2016-10-27 54855.8001       99        10435.9997
2016-10-26 41749.8009       76        10435.9997
2016-10-25 46626.8001       79        10435.9997
2016-10-24 38678.8017       76        10435.9997
2016-10-22 30351.9997       48        10435.9997

问题在于“RebuySum”列是对上述所有日期的总和进行分组的。作为“SumByReceipt”，我希望它按日期分组，而不是每行的总和。

我已经反复尝试分组和求和，并让它工作，但它却弄乱了“SumByReceipt”列。

非常感谢有关此方面的想法。

【问题讨论】：

标签： mysql sql-server join group-by cross-join

【解决方案1】：

按日期对子查询进行分组，然后按日期加入。

SELECT tr.SoldDate, SUM(tr.TotalAmount) as SumByReceipt,
        COUNT(DISTINCT(tr.`ForsNr`)) as TotalCustomers, IFNULL(rebuy.RebuySum, 0) RebuySum
FROM transactions tr   
LEFT JOIN (
    SELECT SoldDate, SUM(TotalAmount) as RebuySum
    FROM transactions_rebuy
    WHERE SoldDate BETWEEN '2016-10-22' AND '2016-10-27'
    GROUP BY SoldDate
    ) as rebuy
ON tr.SoldDate = rebuy.SoldDate
WHERE tr.SoldDate BETWEEN '2016-10-22' AND '2016-10-27' 
GROUP by tr.SoldDate
ORDER by tr.SoldDate DESC

【讨论】：