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Upmerge

Posted on 2004-10-17
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What is the benifit of using 'upmerge' command introduced in oracle 9i & how it works?
it is my open book bonus question in University i need it's expert answer as soon as possible.
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Question by:Fahad_Hafeez
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morphman earned 125 total points
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You mean the MERGE command, or commonly called the "upsert". It is essentially 2 commands in 1, commonly used in ETL transformations. Basically the common operation is

"I want to update existing records, and create new records where a record doesnt already exist".

The merge command providess this functionality in 1 command , MERGE. In 8i SQL you would have to perform 2 statements. An UPDATE followed by an INSERT. This requires 2 table scans as opposed tot he MERGE commands single scan.

Hope this helps,
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