我需要通过SN号将消耗值基于前一个消耗值.这是我的数据:
表EnergyLog
SN Date Value
2380 2012-10-30 00:15:51 21.01
2380 2012-10-31 00:31:03 22.04
2380 2012-11-01 00:16:02 22.65
2380 2012-11-02 00:15:32 23.11
20100 2012-10-30 00:15:38 35.21
20100 2012-10-31 00:15:48 37.07
20100 2012-11-01 00:15:49 38.17
20100 2012-11-02 00:15:19 38.97
20103 2012-10-30 10:27:34 57.98
20103 2012-10-31 12:24:42 60.83
这是我需要的结果:
SN Date Value consumption
2380 2012-10-30 00:15:51 21.01 0
2380 2012-10-31 00:31:03 22.04 1.03
2380 2012-11-01 00:16:02 22.65 0.61
2380 2012-11-02 00:15:32 23.11 0.46
20100 2012-10-30 00:15:38 35.21 0
20100 2012-10-31 00:15:48 37.07 1.86 …