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From: tshad on 17 Mar 2010 21:59
I ran the Engine Tuning on my Tuning trace for a page that is a little slow.

It seemed that indexes were fine but was still a bit slow.

The Recommenations are only to create statistics, 2 on one table and 7 on
another table.

When I put my mouse over the Target of Recomendation, I get something like:

***********************************
Update New Statistics
[MarginID], [CustomerID]
***********************************

***********************************

Update New Statistics
[Orders],[MarginID], [CustomerID]
************************************

So I would do something like:

CREATE STATISTIC CustomerOrdersMarginIDCustomerID
ON CustomerOrders (MarginID, CustomerID)

and

CREATE STATISTIC CustomerOrdersMarginIDCustomerID
ON CustomerOrders (Orders,MarginID, CustomerID)

So if I add these statistics, do I need to update statistics as well or does
it do it as I Create them.

Also, are they updated as new changes are made to the tables or do you need
to run UPDATE STATISTICS to update them. Some of the write ups I saw said
you shouldn't do it too often because when you do, all the stored procedures
would be recompiled.

Also, there are a few _WA_SYS_... object which are Auto Created Statistics.
And none of them are these. Why did it create the others and not these?

If I create all the new ones, is this going to slow the system down?

Is there any downside to creating them - just because DTA suggested it?

Thanks,

Tom


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