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Message Posted: Wed, 31 Oct 2001 @ 16:35:14 GMT


     
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Subj:   Re: NULL vs NOT NULL - PERFORMANCE ISSUES
 
From:   Eric J. Kohut

Dave made some good points but missed one important one.

There is extra logic for many queries if the query has to deal with nulls. Sometimes this can be a few extra steps in a query plan for any joins, sub-queries, etc...

Also, I would specifically check on the issue with using columns containing nulls in sub-queries. I believe that this may still be a bad choice. I've not heard anything to change this. You can use a correlated sub-query with a not exist to get around the issue, but this may mean changing your SQL.

Good Luck,

Eric

EJK
Eric J. Kohut
Senior Solutions Consultant - Teradata Solutions Group - Retail
Certified Teradata Master
NCR Corp.



     
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