我在构建聚合函数时遇到问题。这是我的问题：
我有一张这样的表
id action day isSum difference
1 ping 2012-01-01 1 500 (this is the sum of the differences from last year)
2 ping 2012-01-01 0 -2
3 ping 2012-01-02 0 1
4 ping 2012-01-03 0 -4
5 ping 2012-01-04 0 -2
6 ping 2012-01-05 0 3
7 ping 2012-01-06 0 2
8 ping 2012-01-01 1 0 (this is the sum of the differences from last year, now for pong)
9 pong 2012-01-01 0 -5
10 pong 2012-01-02 0 2
11 pong 2012-01-03 0 -2
12 pong 2012-01-04 0 -8
13 pong 2012-01-05 0 3
14 pong 2012-01-06 0 4
我现在需要选择每天01-01以来的操作，日期和汇总差异，以便我的结果看起来像这样
action day total
ping 2012-01-01 498
ping 2012-01-02 499
ping 2012-01-03 495
ping 2012-01-04 493
ping 2012-01-05 496
ping 2012-01-06 498
pong 2012-01-01 - 5
pong 2012-01-02 - 3
pong 2012-01-03 - 5
pong 2012-01-04 -13
pong 2012-01-05 -10
pong 2012-01-06 - 6
我该怎么做？
有很多数据集（ ~1百万），因此查询需要相当便宜。根据行动栏，我不知道使用金额如何获得每日记录的每日总和。