what is explain and how does it work?

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Madhulathamadduri  

 Profile Answers by Madhulathamadduri Questions by Madhulathamadduri

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

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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

 Profile Answers by senthang Questions by 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 ...

yuvaevergreen

 Profile Answers by yuvaevergreen Questions by yuvaevergreen

• Jun 6th, 2011

Explain statement generally gives the step by step analysis of the queries being executed in the database. It is the plan prepared by PE dispatched to the amps. It could also identify intermediate sp...

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Rakesh

• Jul 26th, 2017

Rule 1: Information Rule The data stored in a database, may it be user data or metadata, must be a value of some table cell. Everything in a database must be stored in a table format. Rule 2: Guar...

Ankal

• Oct 14th, 2011

11 1/2 or 12 codd's rules support

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