median - 计算 PostgreSQL 时态数据库中每小时时间片的中位数

Question

我正在研究时态数据库。我需要在时间序列数据中完成聚合。我应该找到可以是 Hour:00、Hour:01 或 Hour-1:59 的瞬时小时数，并提取与瞬时小时数前后 5 分钟相关的对应观察值。因此，从上述 5 个候选中提取中值。

Sample data1                                           

 Time&Date(timestamps)              Surface_Temprature
2012-11-02 00:45:09+02                  -1.770
2012-11-02 00:47:09+02                  -1.780
2012-11-02 00:49:09+02                  -1.500
2012-11-02 00:51:09+02                  -1.460
2012-11-02 00:53:09+02                  -1.720
2012-11-02 00:55:09+02                  -1.670
2012-11-02 00:57:09+02                  -1.560
2012-11-02 00:59:09+02                  -1.690
2012-11-02 01:01:09+02                  -1.970
2012-11-02 01:03:09+02                  -1.790
2012-11-02 01:05:09+02                  -1.790
2012-11-02 01:07:09+02                  -1.840
2012-11-02 01:09:09+02                  -1.910
2012-11-02 01:11:09+02                  -1.870


Sample Data2:

Date&Time (Timestamps)                  SurfaceTemprature                      
2007-09-28 23:46:14+02                  -1.320                 
2007-09-28 23:48:14+02                  -1.460                 
2007-09-28 23:50:14+02                  -1.620                 
2007-09-28 23:52:14+02                  -1.670                 
2007-09-28 23:54:14+02                  -1.640                 
2007-09-28 23:56:14+02                  -1.700                 
2007-09-28 23:58:14+02                  -1.810                 
2012-11-03 00:00:14+02                  -1.890                 
2012-11-03 00:02:14+02                  -1.790                 
2012-11-03 00:04:14+02                  -1.780                 
2012-11-03 00:06:14+02                  -1.660                 
2012-11-03 00:08:14+02                  -1.680                 
2012-11-03 00:10:14+02                  -1.900                 
2012-11-03 00:12:14+02                  -1.820                 
2012-11-03 00:14:14+02                  -1.780                 
2012-11-03 00:16:14+02                  -1.940                 
2012-11-03 00:18:14+02                  -1.900   

有谁能帮助我吗？

Answer 1

这样的事情应该做

SELECT 
  EXTRACT(HOUR FROM mytimestamp) AS hour,
  PERCENTILE_CONT(0.5) WITHIN GROUP(ORDER by temperature) AS median 
FROM mytable GROUP BY EXTRACT hour;