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what is explain in teradata?
what is explain and how does it work?
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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 ...
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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Teradata performance tuning and optimization
what is an optimization and performance tuning and how does it really work in practical projects. can i get any example to better understand.
tdguy
- May 22nd, 2013
Performance tuning:
1. Look at the plan generated by PE.
2. Check for the recommendations of stats to be collected for the columns.
3. Try to avoid product joins and unnecessary joins.
4. Try to avoid casting in join conditions
5. Use secondary index appropriately.
6. Use join index if necessary.debashish.munshi
- Sep 18th, 2012
Optimization of queries improves performance of TD and helps the PE to generate the most efficient execution plan. To Optimize a query, choose the Primary Index to avoid skrew, Collect statistics on t...
