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Delete oldest records after maximum row count is reached in a SQL Server table?

Posted on 2012-03-20
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Last Modified: 2012-03-30
(Need an answer for either SQL Server 2005 or 2008.)

I have a SQL Server table whose size I want to limit.  I want to be able to specify that only, say, 50,000 records are allowed.  I do not want to prevent the addition of new records.  Rather, I want to drop the oldest records as new records are added so that I retain only the most recent 50,000.

Each record has an auto-incremented field with an increment of 1.  It is possible I could be inserting hundreds of records at once, several times a day.

I am guessing this could be handled by some type of insert trigger.  I would also consider some kind of scheduled process that would run each day (or week) and simply delete all the unwanted records at that time to keep reducing the record count to 50,000.

Thanks.
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Question by:AutomateMyOffice
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amit_g earned 2000 total points
ID: 37743547
You could use the script below but this should certainly be not run as a trigger. Why would you want to slow down every single insert. Run it as a job daily or if the row count is very important to keep low, every hr or so...

delete TableName
from TableName T1
inner join (
	select ROW_NUMBER() OVER (order by AutoID desc) RowNum, AutoID  from TableName
) T2 on T1.AutoID = T2.AutoID
where T2.RowNum > 50000

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Author Comment

by:AutomateMyOffice
ID: 37743643
I definitely want to accomplish this in the most efficient way.  What is the best approach for scheduling such a thing?  Would I create the script as a stored procedure?  Please be as detailed as possible.  Thanks very much!
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Expert Comment

by:amit_g
ID: 37743713
Yes make it a stored procedure. First test it in a test environment and then make it a SQL job that runs at every x hrs/days.
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Author Comment

by:AutomateMyOffice
ID: 37743731
I have tested it and it works perfectly.  I am sorry but I still need help in how to make and schedule a "SQL job."  Thanks.
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Author Comment

by:AutomateMyOffice
ID: 37743799
Oh-oh.  I did a little research and it looks like a scheduled job demands SQL Server AGENT, which is not available in my SQL Server EXPRESS environment.  Is there an alternative approach?
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Expert Comment

by:amit_g
ID: 37743801
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Expert Comment

by:amit_g
ID: 37743871
You can use the SqlCmd and schedule the windows job. The command line would be

sqlcmd -S ServerName\SQLExpress -d DatabaseName -Q "exec YourSPName"

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Using the sqlcmd Utility (SQL Server Express)

The instructions to created a windows task would depend on the version of the windows. Here are instructions for Windows 7
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Author Comment

by:AutomateMyOffice
ID: 37788383
Fantastic.  This worked perfectly.  I am running your procedure using sqlcmd in Task Scheduler under Windows 7.  Also, I added a parameter so that the desired number of rows could be specified without having to modify the stored procedure:
 
"exec TruncateTable @MaxRows=$(myparam)" /v myparam=1000

Thanks!
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