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Message Posted: Thu, 17 Jan 2008 @ 13:06:05 GMT


     
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Subj:   Re: Join behaving of a PI join
 
From:   Barry Hull

The reason that it might want to join one of your fact tables to a smaller table is that it thinks by joining to it, it will eliminate some rows. It looks like it wants to join ORDERHEADER to CUSTOMER and when it does this, it has a "no confidence" estimate. Try collecting stats on the CUSTOMER_ID in ORDERHEADER and see if that makes a difference.

The estimates shown are not very large. The optimizer will be more willing to move tables around if it's working with small tables. If your ORDERHEADER and ORDERDETAIL were much larger, then the optimizer will tend to join them together before moving them around.


Hope that helps.

Barry



     
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