Home Page for the TeradataForum

Archives of the TeradataForum

Message Posted: Wed, 09 Mar 2005 @ 21:41:16 GMT

  <Prev Next>   <<First <Prev Next> Last>>  

Subj:   Re: Use of Indexes in Teradata


It all depends on the cardinality .. NUSIs are equally good and bad . It all depends on percent of rows per NUSI values . If you have more rows that qualify NUSI value then you will end up reading almost each and every data block , the no: of I/O operations undertaken by the retrieval could easily exceed the number required for a FTS (full table scan).. So in these cases table scans are much more efficient then NUSI access

So we cannot just go with a thumb rule that NUSIs are always good . You need to closely look into data demographics for NUSI creation

Hope this helps



  <Prev Next>   <<First <Prev Next> Last>>  
  Top Home Privacy Feedback  
Copyright for the TeradataForum (TDATA-L), Manta BlueSky    
Copyright 2016 - All Rights Reserved    
Last Modified: 28 Jun 2020