Question

我有两个要计算的汇总子查询。该查询在不进行最终计算的情况下仍能正常工作，但是当我从两个子查询中添加总和计算时，会将其全部归为一个总和。

设置为两个表，其中一个表（父母付款）具有我要分组以获取总付款的付款。另一个（服务日志）已发送时间和该时间的费率。该服务已发布给孩子，因此我需要从孩子那里查找父母ID。我需要总余额，所以我要找到“已计算的到期”和“已付款”之间的差异。

我正在使用的查询是：

SELECT PID, b.Due, a.Paid, SUM(b.Due - a.Paid) FROM 
(SELECT Person AS par, SUM(Amount) AS Paid FROM parentpayments GROUP BY pp.Person) AS a 
JOIN 
(SELECT p.ID AS PID, SUM(l.Time * l.Rate) AS Due FROM servicelog AS l INNER JOIN children AS c ON c.ID = l.Child INNER JOIN people AS p ON p.ID = c.Parent GROUP BY p.ID) AS b 
ON PID = Par

这可能吗？

Answer 1

外部查询中不需要SUM()。 PID和Par在子查询中已经是唯一的。因此，将其中之一分组是没有意义的。但是，如果在不使用GROUP BY的情况下使用SUM（），则只会得到一行，并且选择PID，Due和Paid毫无意义。因此，您只需要删除SUM()：

SELECT PID, b.Due, a.Paid, b.Due - a.Paid FROM 
(SELECT Person AS par, SUM(Amount) AS Paid FROM parentpayments GROUP BY pp.Person) AS a 
JOIN 
(SELECT p.ID AS PID, SUM(l.Time * l.Rate) AS Due FROM servicelog AS l INNER JOIN children AS c ON c.ID = l.Child INNER JOIN people AS p ON p.ID = c.Parent GROUP BY p.ID) AS b 
ON PID = Par

尽管可以使用查询并附加GROUP BY PID。但这与按主键分组一样。每个组仅包含一行。 SUM（）等于其参数。

还有另一种方法可以达到相同的结果。您可以使用UNION代替JOIN-并且您将需要SUM()。请注意，在这种情况下，您无法分别选择Due和Paid-仅选择余额：

SELECT PID, SUM(amount) as balance
FROM (
    SELECT Person AS PID, SUM(Amount) AS amount
    FROM parentpayments
    GROUP BY pp.Person
    UNION ALL
    SELECT p.ID AS PID, -SUM(l.Time * l.Rate) AS amount
    FROM servicelog AS l
    INNER JOIN children AS c ON c.ID = l.Child
    INNER JOIN people AS p ON p.ID = c.Parent
    GROUP BY p.ID
) AS x
GROUP BY PID

从两个联接的聚合查询中计算

1 个答案: