SQL windows 使用 MAX 的函数未给出预期结果

Question

所以我正在玩弄 SQL window 函数，遵循使用 AdventureWorks 2012 的在线帮助教程。

我从下面的查询中选择了数据到一个新的 table

SELECT sh.CustomerID AS AccountID,
sd.SalesOrderDetailID AS TransactionID,
sh.OrderDate AS TransactionDate,
sd.LineTotal AS Amount
INTO Transactions
FROM sales.SalesOrderHeader sh INNER JOIN sales.SalesOrderDetail sd on
            sh.SalesOrderID = sd.SalesOrderID

然后我运行下面的查询：

select *,
MIN(Amount) OVER(Partition by AccountID order by transactionDate) AS     MinOrderForDate
from dbo.transactions
Order by AccountID, transactionID desc

这给了我预期的结果：

AccountID   TransactionID   TransactionDate         Amount      MinOrderForDate
11000       63804           2007-11-04 00:00:00.000 53.990000   4.990000
11000       63803           2007-11-04 00:00:00.000 34.990000   4.990000
11000       63802           2007-11-04 00:00:00.000 4.990000    4.990000
11000       63801           2007-11-04 00:00:00.000 28.990000   4.990000
11000       63800           2007-11-04 00:00:00.000 2384.070000 4.990000
11000       38716           2007-07-22 00:00:00.000 21.980000   21.980000
11000       38715           2007-07-22 00:00:00.000 2319.990000 21.980000
11000       449             2005-07-22 00:00:00.000 3399.990000 3399.990000
11001       115673          2008-06-12 00:00:00.000 34.990000   4.990000
11001       115672          2008-06-12 00:00:00.000 8.990000    4.990000
11001       115671          2008-06-12 00:00:00.000 4.990000    4.990000
11001       115670          2008-06-12 00:00:00.000 539.990000  4.990000
11001       38639           2007-07-20 00:00:00.000 8.990000    4.990000
11001       38638           2007-07-20 00:00:00.000 53.990000   4.990000
11001       38637           2007-07-20 00:00:00.000 9.990000    4.990000
11001       38636           2007-07-20 00:00:00.000 4.990000    4.990000
11001       38635           2007-07-20 00:00:00.000 21.980000   4.990000
11001       38634           2007-07-20 00:00:00.000 2319.990000 4.990000
11001       423             2005-07-18 00:00:00.000 3374.990000 3374.990000

但是，当我将 MIN 替换为 MAX 时，我一直在获取帐户的整个数据运行ge 的 MAX 值，但我不明白为什么？

select *,
MAX(Amount) OVER(Partition by AccountID order by transactionDate) AS       MaxOrderForDate
from dbo.transactions
Order by AccountID, transactionID desc


AccountID   TransactionID   TransactionDate         Amount      MaxOrderForDate
11000       63804           2007-11-04 00:00:00.000 53.990000   3399.990000
11000       63803           2007-11-04 00:00:00.000 34.990000   3399.990000
11000       63802           2007-11-04 00:00:00.000 4.990000    3399.990000
11000       63801           2007-11-04 00:00:00.000 28.990000   3399.990000
11000       63800           2007-11-04 00:00:00.000 2384.070000 3399.990000
11000       38716           2007-07-22 00:00:00.000 21.980000   3399.990000
11000       38715           2007-07-22 00:00:00.000 2319.990000 3399.990000
11000       449             2005-07-22 00:00:00.000 3399.990000 3399.990000
11001       115673          2008-06-12 00:00:00.000 34.990000   3374.990000
11001       115672          2008-06-12 00:00:00.000 8.990000    3374.990000
11001       115671          2008-06-12 00:00:00.000 4.990000    3374.990000
11001       115670          2008-06-12 00:00:00.000 539.990000  3374.990000
11001       38639           2007-07-20 00:00:00.000 8.990000    3374.990000
11001       38638           2007-07-20 00:00:00.000 53.990000   3374.990000
11001       38637           2007-07-20 00:00:00.000 9.990000    3374.990000
11001       38636           2007-07-20 00:00:00.000 4.990000    3374.990000
11001       38635           2007-07-20 00:00:00.000 21.980000   3374.990000
11001       38634           2007-07-20 00:00:00.000 2319.990000 3374.990000
11001       423             2005-07-18 00:00:00.000 3374.990000 3374.990000

我做错了吗？

Answer 1

您正在按 AccountID 进行分区。它为您提供该 AccountID 的 MAX。对于 AccountID 11000，MAX 为 3399，对于 AccountID 11001，MAX 为 3374。

Answer 2

您的意图不是很明确，但听起来您希望每个 account/transactionDate 分组都有 min/max。如果是这种情况，您可能不是要将 transactionDate 放在 window 函数的 order by 子句中。

我想你是想这样做：

MIN(Amount) OVER(Partition by AccountID, transactionDate) AS MinOrderForDate
MAX(Amount) OVER(Partition by AccountID, transactionDate) AS MaxOrderForDate

Answer 3

如果您按非唯一列排序，则无法保证结果集。

在您的情况下，结果正是您所要求的，累积 MIN/MAX，由于 ORDER BY，ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW 自动添加到您的查询中。此外，窗口聚合函数中的 ORDER BY 与最终的 ORDER BY 不同，这增加了更多的混淆。

你没有明确说明你想要得到什么。根据列别名，您可能需要 "group" MIN/MAX:

MIN(Amount) OVER(Partition by AccountID, transactionDate) AS     MinOrderForDate

SQL windows 使用 MAX 的函数未给出预期结果

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