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What EXPLAIN does in Teradata, what is High confidence, Low
confidence and No confidence.. And How we improve the query
performance .
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Answer Posted / yuvaevergreen
The explain generally displays the plan which would be
prepared by Optimizer.We can say that(though not accurate)
plan would be the steps followed by Teradata to solve a
query.Confidence levels indicate how well the optimizer is
aware about the demographic data for a particular step.
>>High confidence: Means the optimizer know about the no of
rows that would be returned as a result of that step.
Examples would be when PI statistics exist when the column
or range stats exist or no join involved.
>>Low confidence: Some stats available. Join and stats
available on both sides of the join.
>>No confidence: No stats available. Join involved.
| Is This Answer Correct ? | 8 Yes | 1 No |
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