Answered Questions

  • MultiSet Table and Duplication

    Why fastload does not support multiset table and duplication?

    saiteja

    • Jun 16th, 2017

    Fastload does not support duplicates because storing duplicates in fastload is difficult to the system decreases the performance of the fastload when the fastload script fails when you restart the fastload script and the same row hash value is loaded in to second time

  • Join Stratagies

    There are 2 tables, table A with 10 million records, table B has 100 million records, now we are joining both tables, when we seen Explain Plan the plan showing TD will took the table A and it will redistributes itNow the Question is: By that plan is the optimizer is correct job or not ? Justify Ans2. From the same above example now the optimizer is taking Table B (100 million records) and it is distributing...

    yuvaevergreen

    • May 22nd, 2013

    Merge join strategies are 1. Big and small table joins - duplicate small tables 2. Column used in join is PI for one table - redistribute the other table in spool. 3. Column used in join is non PI f...

    • Sep 18th, 2012

    There are 2 tables, table A with 10 million records, table B has 100 million records, now we are joining both tables, when we seen Explain Plan the plan showing TD will took the table A and it will re...

  • what is explain in teradata?

    what is explain and how does it work?

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    Editorial / Best Answer

    Madhulathamadduri  

    • Member Since Jan-2010 | Apr 15th, 2011


    The EXPLAIN modifier preceding an SQL statement generates an
    English translation of the optimizer’s plan. It is fully parsed and
    optimized, but not executed.
    EXPLAIN returns:
    Text showing how a statement will be processed (a plan).
    An estimate of how many rows will be involved.
    A relative cost of the request (in units of time).
    This information is useful for:
    • Predicting row counts.
    • Predicting performance.
    • Testing queries before production.
    • Analyzing various approaches to a problem.
    EXPLAIN may also be accessed using Teradata Visual Explain.

    senthang

    • Jun 22nd, 2011

    1. English version on optimizer plan2. to identify the objects used and kind of locks applied on those objects3. to identify the number of amp operation eg. single ot group amp4. to identify the data ...