Hi frnds this question is asked at IBM One query is there when we dont collect

Hi frnds this question is asked at IBM
One query is there when we dont collect stastics on
it,exlapin will show us LOW CONFIDENCE,When we collect
stastics it shows HIGH CONFIDENCE.WHAT IS THE INTERNAL
ARCHITECTURE ACTUALLY GOING ON ?????ASKED ON 23-08-2012

THANKS IN ADVANCE

Question Posted / gowthami8.b

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Hi frnds this question is asked at IBM One query is there when we dont collect stastics on it,exl..

Answer / tdguy

statistics collection is a concept, where TD stores the
demographic data and stores. When generating the explain
plan, TD looks for the stats for the columns used in the
sql., particularly the columns used on both sides of the
join. TD prepares a estimate based on the data available.If
enough stats are not available, TD displays a low
confidence. Whereas, if stats are collected for columns
involved in sql, stats will be available for TD, which in
turn displays a high confidence, which means exact or close
approximate no of rows processed will be displayed.

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Hi frnds this question is asked at IBM One query is there when we dont collect stastics on it,exl..

Answer / rkraju

when we collect stats the demographic information stored on
table header.so the optimizer picks the stats information
from the table header for generating plan for a given query.

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