我如何使用SUM()OVER()

Question

我无法理解这段代码的错误

ID      AccountID       Quantity
1          1               10           Sum = 10
2          1               5                = 10 + 5 = 15
3          1               2                = 10 + 5 + 2 = 17
4          2               7                = 7
5          2               3                = 7 + 3 = 10  

SELECT ID, AccountID, Quantity, 
       SUM(Quantity) OVER (PARTITION BY AccountID ) AS TopBorcT, 
FROM tCariH

Answer 1

好像您希望查询返回运行总计,但它必须为两个分区提供相同的值AccountID.

要获得运行总计SUM() OVER (),需要在之后添加ORDER BY子句PARTITION BY …,如下所示:

SUM(Quantity) OVER (PARTITION BY AccountID ORDER BY ID)

但请记住,并非所有数据库系统都支持窗口聚合函数ORDER BY的OVER子句.(例如,SQL Server直到最新版本SQL Server 2012才支持它.)

Answer 2

如果你使用SQL 2012,你应该尝试

SELECT  ID, 
        AccountID, 
        Quantity, 
        SUM(Quantity) OVER (PARTITION BY AccountID ORDER BY AccountID rows between unbounded preceding and current row ) AS TopBorcT, 
FROM tCariH

如果可用,按日期列更好的排序.

Answer 3

查询将是这样的：

SELECT ID, AccountID, Quantity, 
       SUM(Quantity) OVER (PARTITION BY AccountID ) AS TopBorcT 

       FROM #Empl ORDER BY AccountID

Partition by 与 group by 类似。这里我们按 AccountID 分组，因此 sum 将对应于 AccountID。

第一种情况， AccountID = 1 ，然后 sum(quantity) = 10 + 5 + 2 => 17 & For AccountID = 2，然后 sum(Quantity) = 7+3 => 10

所以结果看起来像附加的快照。