下面这个代码可以吗？
select date, time, wind_code, totalvolume - nullFill!(move(totalvolume, 1), 0) from a context by date, wind_code
eachPre函数将给定函数/运算符应用于X中所有相邻的数据对，它可以指定初始值：
select date, time, wind_code, eachPre(-, totalvolume, 0) as deltaVol from a context by date, wind_code
