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Message Posted: Fri, 22 Nov 2002 @ 19:26:42 GMT


     
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Subj:   Re: More Statistics Questions
 
From:   Frank C. Martinez IV

Hijola! Come on people, Teradata 101 again!

Primary indices are used first for distribution, then for joining. Having multi-column primary's can be a good thing, but remember what they're there for. Normal Teradata indices require the value, the whole value (meaning all the columns) and nothing but the value (meaning NULLs don't cut it). Well, at least you're using the EXPLAIN, which is a cool, necessary and usually neglected idea (First question to someone who asks "Why is my query running long?" is "Did you do an EXPLAIN?"). Yes, most indicies that aren't primary don't do a dang thing except sit there and make the dba happy ("Look Ma, I put indices on that table!"). So the procedure is: run the query; run the explain; add the index; run the explain;, run the query.

Now, somebody wanted continue the discussion with VALUE ORDERed queries?

iv



     
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