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Message Posted: Tue, 05 Jun 2001 @ 13:49:38 GMT


     
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Subj:   TeraData's optimizer
 
From:   Ruth Fenwick

Does anybody have experience with how the optimizer evaluates BETWEEN?

I have a large table, 921 million rows. Table has a NUSI on it of date, with about 20 months worth of daily data. There are current statistics on the table.

If a user writes a query using a between as in scan_date between May 19 and May 21, Teradata will do a table scan, if it's written as scan_date = may 19 or scan_date = may 20 or scan_date = may 21, Teradata uses the index.

If it's written as scan_date >= May 19 and Scan_date <= may 21, Teradata does a full table scan

If it's written as scan_date in (may19, may 20, may 21), Teradata uses the index

So what does everyone do? Do you just recommend that we never user BETWEEN?

Ruth Fenwick
Hudson's Bay Company



     
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