Question

I have a table like this:

ModuleID   TimeStamp           Value   TotalPerDay
1          8/5/2012 9:00 PM    0.25     0.25
2          8/5/2012 9:00 PM    0.15     0.15
3          8/5/2012 9:00 PM    0        0
4          8/5/2012 9:00 PM    1.25     1.25
1          8/5/2012 10:00 PM   0.05     0.30
3          8/5/2012 10:00 PM   0.89     0.89
4          8/5/2012 10:00 PM   0.14     1.39
4          8/5/2012 11:00 PM   0.70     2.09
4          8/5/2012 12:00 PM   0.43     2.52
...

And I have 15000 modules updating this table every hour. In addition, at midnight, the TotalPerDay values get reset.

I am struggling with a query that should pull the latest TotalPerDay value for a given set of ModuleID‘s.

I tried using a GROUP BY clause on ModuleID. But how can I retrieve the latest TotalPerDay value without using an aggregating function?

By the way, I am using SQL Server 2008.

Thanks in advance!

Answer 1

If I understand your question correctly, then this should give you the latest total per day by module (if time stamp is unique):

; with MyCte (moduleId, TimeStamp)
AS(
    select moduleId, max(TimeStamp)
    from modules
    group by moduleId
)
select * from modules a
join MyCte b
on a.moduleId = b.moduleId
    and a.TimeStamp = b.TimeStamp 

Based on your comments to Gordon, you are looking for a SUM per Day per module? If yes, then here you go:

select ModuleId, 
       convert(varchar,cast(TimeStamp as datetime),101),
       sum(totalPerDay) as GrandTotal
from modules
group by ModuleId, convert(varchar,cast(TimeStamp as datetime),101)