how to detect skew in a column?

From: Josh Collier <Josh.Collier_at_Banfield.net>
Date: Thu, 11 Mar 2004 11:20:02 -0800
Message-ID: <219647973E94D211A8F20008C709725211D6B646@mercury.hq.vetsmart.com>

Greetings,

I am trying to write some perl to query the database and spit out list of candidate columns for histograms. I know that dbms_stats has the SKEWONLY method opt, but that also builds histograms automatically, I don't want to do that, just want candidates that I can look investigate. I've traced a dbms_stats session with method opt 'SKEW ONLY', so I think I see how dbms_stats detects skew, but I'm still investigating.

Any ideas how to identify columns that have skew in them? Besides the eyeball approach: select count(*),val from table group by val and examine the result set.

josh

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Received on Thu Mar 11 2004 - 14:39:41 CST