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Teradata - How Teradata Retrieves Rows ?




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asked vishnoiprem August 17, 2014 05:00 AM  

How Teradata Retrieves Rows ?


           

1 Answers



 
answered By vishnoiprem   0  
SELECT *
FROM Employee
WHERE EMP = 99;

In the example above, a user runs a query looking for information on Employee 99.

The PE sees that the Primary Index Value EMP is used in the SQL WHERE clause. Because
this is a Primary Index access operation, the PE knows this is a one AMP operation. The
PE hashes 99 and the Row Hash is 00001111000011110000111100001111. This points
to a bucket in the Hash Map that represents AMP 4. AMP 4 is sent a message to get the
Row Hash: 00001111000011110000111100001111 and make sure itÂ’s EMP 99.
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