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Message Posted: Tue, 07 Aug 2012 @ 16:30:51 GMT


     
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Subj:   Concept of Index Only Scans in Teradata?
 
From:   Nathan_S_Smith

Hi,

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?

For example, a table defined as:

ColA,
ColB,
ColC,
ColD,
Many more columns.


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?

Are join indexes the only type of index where the columns in the query matching the columns in the index affect the choice of the index over the base table?


Thanks,

Nathan



     
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