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Message Posted: Wed, 16 Nov 2005 @ 14:40:11 GMT


     
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Subj:   UPDATE vs DELETE-INSERT
 
From:   Agarwal, Rishi

Hi,

What is the ideal way of handling UPDATE on large table in Teradata?

Assuming the following scenario:

     UPDATE TABLE1 A
     FROM TABLE2 B
     SET col3 = B.col3,
         Col4 = B.col4
     WHERE
           A.col1 = B.col1
       AND A.col2 = B.col2
     ;

1. Will there be any performance issue even if the Join is on PI columns (col1, col2 are defined)?

2. If yes, If we do DELETE-INSERT in this case, will it have any performance gain over UPDATE as the joining condition is going to be same here (on PI columns).

There are many threads on the fast path for UPDATE/DELETE. These suggest to do INSERT-SELECT into empty table and then swap this new table with the Old table and drop the Old table. Is there any other way other than dropping the main table.


Thanks

Rishi



     
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