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Message Posted: Mon, 09 Jun 2003 @ 19:45:02 GMT


     
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Subj:   To Cover or not to Cover..
 
From:   Jim Renner

...That is the question.

Ok, so I am forgetting my Teradata 101...I would like to ask the group if there are any drawbacks to creating an index to cover a set query.

My example: I have a couple of tables which are both created with a column (ID) as the primary index...and this is the same column where my joins occur.

If I run my query against these two tables 2.6Mil x 78000 rows, it takes around 31 minutes to complete.

If I run create index (ID) order by Hash (ID) on <> the querry takes around 28 seconds.

As you can see, the savings is substantial, but the question is...at what cost. Would a query not using the (ID) column suffer? Or is the cost merely storage and maintenace of stats on the new index?

Thank you for the Teradata 101 refresher.



     
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