如何编写SQL LAG查询来获取运行总计的最大值？

Question

例如如果为运行总计求和的值有时为负数，则运行总计可能会下降。但对于每一行，我还希望达到该点的最大运行总数...

如何对此代码进行增强？

select ItemId, DateId, TargetRunningStock, 
       sum(TargetRunningStock) over (partition by itemid order by dateid)
from WarehouseData

Answer 1

您可以添加另一个级别：

select ItemId, DateId, TargetRunningStock, RunTot,
       Max(RunTot) over (partition by itemid order by dateid) as MaxRunTot
from (
  select ItemId, DateId, TargetRunningStock, 
       sum(TargetRunningStock) over (partition by itemid order by dateid) as RunTot
  from WarehouseData
) Step1