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Teradata - What are UPI and NUPI ?




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asked vishnoiprem August 17, 2014 04:36 AM  

What are UPI and NUPI ?


           

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answered By vishnoiprem   0  
Unique Primary Index (UPI)

A Unique Primary Index means that the values for the selected column must be unique.
The data will always be spread evenly if the Primary Index is unique. If you try and
insert a row with a Primary Index value that is already in the table, the row will be
rejected. Even though a Unique Primary Index will always spread the table rows evenly
amongst the AMPs, please don’t assume this is always the best thing to do.

A Unique Primary Index (UPI) will always spread the rows of the table Evenly amongst
the AMPs. UPI access is always a one-AMP operation. It also requires no duplicate row
checking.

Non-Unique Primary Index:

A Non-Unique Primary Index (NUPI) means that the values for the selected column can
be non-unique. You can have many rows with the same value in the Primary Index. A
Non-Unique Primary Index will almost never spread the table rows evenly. Please don’t
assume this is always a bad thing.
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