October 12, 2008 08:40pm pdt

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	[x] Attachment Details

speeding up a query

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5.6

Zones: MS SQL Server, SQL Server 2005

Hi,

I have a table with the following structure:

location_id int
start_date datetime
end_Date datetime
object_id int

The table models the location of each object in the system depending on time. I am using this query to determine the number of objects at a location given a date (parameter @date):

select count(distinct object_id) from table where (start_date <= @date and end_date >= @date) or ( start_date <= @date and end_date is null)

I am using distinct to count each object only once (there is a chance that an object leaves and returns the same day).

Unfortunately, this query takes quite a long time. I am just wondering whether someone could make some suggestions to speed things up.

- What would be the best index for this situation.
- Would it be worthwhile to normalise this table a bit more?

Any suggestions would be very much appreciated. Many thanks in advance.

BW

C

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