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Message Posted: Tue, 07 Aug 2012 @ 19:07:40 GMT


     
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Subj:   Re: Concept of Index Only Scans in Teradata?
 
From:   Dieter Noeth

Nathan_S_Smith wrote:

  Some DBMSs will recognize when a query can be resolved by retrieving data only by scanning a secondary index without having to retrieve data from the base table.  


  Does Teradata apply a similar concept?  


Of course, you'll see it in Explain: ... by way of index #n without accesing the base table ...


  With a PI on ColA and a NUSI on ColC,ColD, if a query selected only ColC and ColD would the query do a single AMP query against the index or would it still use the base table?  


It will use the index but NUSI access is All-AMPs not single AMP.


Dieter



     
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