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Message Posted: Tue, 05 Jul 2011 @ 16:16:57 GMT


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Subj:		Re: Multiset with a UPI

From:		Ramachandran, Janardhan

Hi JK,

Hence, we can not get a Duplicate Row!!! If that is the case, then why use a Multiset? Again, if I m wrong, PLEASE anyone, let me know!

Multiset option is not created only to hold the duplicated rows, It has been created for the performance point of view. As we are in Teradata world we will have the tables with billions of rows and TeraBytes in size. These are tables are going to grow more and more in the future.

If we have only "SET" option in the tables then the system should do duplicate check of all the rows in the table before insert the new row to the table, This is going to give bad performance in pushing the data into the system. By having the "Multiset" option with UPI and USI will avoid the duplicate check and also maintains the uniqueness and does the loading faster.

Thanks & regards

Janardhan R