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Message Posted: Fri, 23 Jan 2004 @ 08:09:16 GMT


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Subj:		Re: Statistics and explain plans

From:		Dieter Noeth

James Judge wrote:

Statistics do not recognize data skewing.

???

Statistics are collected to provide information about data demographics. Within the first intervals the exact row count for highly skewed values may be stored, negative numbers for "Non-modal rows" indicate that:

Interval        Mode Val        Mode Freq       Non-modal rows  Non-modal rows
1:      Davis   Brown   2598    -2      2643
2:      Jones   Johnson 2956    -2      3377
3:      Williams        Smith   5593    -2      3777
4:      Allegra Adams   1354    337     4650
...

Look at the "Teradata Statistis Wizard" manual, chapter 8:

Display and modify the Interval Statistics -> What is a Loner Value?

Dieter