为每个前一行添加值

Question

我有一个 table Grader:

+--------------------------+
|GraderName | Graded_Items |
+--------------------------+
|    A      |       21     |
|    B      |        7     |
|    C      |       17     |
|    D      |       91     |
|    E      |       84     |
|    F      |       52     |
|    G      |       34     |
+--------------------------+

我想把第一行和第二行的SUM放在第二行； SUM第一、二、三行放在第三行；依此类推到其他行。见下文：

+--------------------------------+
|GraderName | Graded_Items       |
+--------------------------------+
|    A      |21                  |
|    B      |21+7                |
|    C      |21+7+17             |
|    D      |21+7+17+91          |
|    E      |21+7+17+91+84       |
|    F      |21+7+17+91+84+52    |
|    G      |21+7+17+91+84+52+34 |
+--------------------------------+

我想达到这个结果：

+--------------------------+
|GraderName | Graded_Items |
+--------------------------+
|    A      |       21     |
|    B      |       28     |
|    C      |       45     |
|    D      |      136     |
|    E      |      220     |
|    F      |      272     |
|    G      |      306     |
+--------------------------+

我试过这个查询：

SELECT Grader,Graded_Items FROM Grader WHERE Grader='A'
UNION ALL
SELECT MAX(Grader),SUM(Graded_Items) FROM Grader WHERE Grader in ('A','B')
UNION ALL
SELECT MAX(Grader),SUM(Graded_Items) FROM Grader WHERE Grader in ('A','B','C')
UNION ALL
SELECT MAX(Grader),SUM(Graded_Items) FROM Grader WHERE Grader in ('A','B','C','D')
UNION ALL
SELECT MAX(Grader),SUM(Graded_Items) FROM Grader WHERE Grader in ('A','B','C','D','E')
UNION ALL
SELECT MAX(Grader),SUM(Graded_Items) FROM Grader WHERE Grader in ('A','B','C','D','E','F')

但是，我的问题是 table 一直在变化，例如 GraderName 在同时填充其对应的 Graded_Items。还有其他方法可以达到我的预期效果吗？

Answer 1

使用 Sum over() 技巧获得运行总数

select GraderName, 
       sum(Graded_Items) over(order by GraderName) As Graded_Items
From yourtable

SQLFIDDLE DEMO

为每个前一行添加值

Adding Values Per Preceding Row

sql

sql-server

sql-server-2012