MySQL 窗函数 流动平均数 running average

AVG(val) OVER (PARTITION BY subject ORDER BY time

ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING)

含义是按照time排序，前后1行加自己后的平均数。

SELECTtime, subject, val,SUM(val) OVER (PARTITION BY subject ORDER BY timeROWS UNBOUNDED PRECEDING)AS running_total,AVG(val) OVER (PARTITION BY subject ORDER BY timeROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING)AS running_averageFROM observations;