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Message Posted: Tue, 20 Jan 2004 @ 18:12:04 GMT

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Subj:   Re: V2R5 Statistics
From:   Victor Sokovin


  So which is efficient and performant.  

  Suppose I had 2 where clauses as follows :  

  1. WHERE col1 = 1 and col2 = 2  

  2. WHERE (col1,col2) = (1,2)  

  In the above case which kind of statistics would/should be used.  

In my opinion, these two syntax forms are optimized in exactly the same way. If there are any differences or bugs in some releases perhaps somebody from NCR could correct me. I personally practically never use the second (vector) form as it never occurred to me that it might offer any additional advantages in performance.

In both cases the multi-column statistics on (col1, col2) should be the most efficient form of statistics. A special case is when there is an SI defined on one of the columns. In that case additional index statistics might also be useful for the optimizer.



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