Meaning of cost in a plan?

From: Jan Nowitzky <nowitzky_at_informatik.uni-jena.de>
Date: Sat, 23 Oct 1999 14:15:57 +0200
Message-ID: <3811A6FD.102225FA@informatik.uni-jena.de>

Hi,

I have following situation.
The plan of my query (Q1) says 'Cost=1237'. Then I have changed the query (Q2) and the new plan says 'Cost=780'. But the response time of Q2 is larger.

Query |  Cost (estimated) | Response Time
 Q1   |        1237       |     123 sec.
 Q2   |         780       |     301 sec.

What is the relevance of the cost in the query plan? What means this cost number in the query plan (which unit)? My statistics are up to date.

Thanx, Jan

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Jan Nowitzky
Friedrich-Schiller-Universität o Institut für Informatik E-Mail nowitzky_at_informatik.uni-jena.de

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Received on Sat Oct 23 1999 - 07:15:57 CDT