Help with a SQL Query

I have been trying to think of a way to retrieve some data from a database by way of a SQL query. I am trying to avoid doing it programatically.

essentially the source table is

ID,DateTime,Count

I want to get the sum of the count for a defined开发者_如何转开发 period of DateTime for each distinct ID within that period.

Any ideas people?

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you want a GROUP BY for this

select ID, sum(Count) as Sum
from yourTable
where DateTime between startDate and endDate
group by ID

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Try something like this:

select ID, sum(Count)
from foo
where [DateTime] between @beginning and @end
group by ID;

This is assuming that you have two variables, @beginning and @end that are typed as DateTime.

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For dates, you should use >= and <, using the start of the period and the start of the next period, like this:

WHERE [DateTime] >= @StartPeriod AND [DateTime] < @StartNextPeriod

..making the whole thing:

SELECT ID, SUM(Count) AS Cnt
FROM dbo.someTable
WHERE [DateTime] >= @StartPeriod AND [DateTime] < @StartNextPeriod
GROUP BY ID;

Otherwise, you run the risk of missing something or including too much.

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SELECT ID, SUM(Count) 
FROM yourTable
WHERE DateTime => '2009-10-01' AND DateTime < '2009-11-01' 
GROUP BY ID;