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Message Posted: Thu, 15 Apr 2004 @ 18:11:53 GMT


     
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Subj:   Resolving the CASE expression
 
From:   Anomy Anom

<-- Anonymously Posted: Thursday, April 15, 2004 13:31 -->

How does Teradata resolves the CASE expression? Why it is not showing in the EXPLAIN plan? Does it use the STATISTICS?

Does it use spool ?. The manual only says it use single pass instead of muliple pass on data to resolve. It doesn't explain how it works. So my question is when it does single pass , does it use the expression from WHERE condition too? otherwise At what point the single pass happening? Is it after the WHERE expression? OR With WHERE expression?

For eg:

        SUM(CASE WHEN table1.column1 in ('a','b') and table2.column2 in ('d','e') THEN 10
                   WHEN ...             THEN 20 END)

Thanks,

Anonym



     
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