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what is a histogram? [message #59154]

Fri, 31 October 2003 13:47

Kapil
Messages: 145
Registered: May 2002

Senior Member

what is a histogram and how does it effects the proformance of a query.

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Re: what is a histogram? [message #59177 is a reply to message #59154]

Sun, 02 November 2003 22:16

Daljit Singh
Messages: 290
Registered: October 2003
Location: Texas

Senior Member

Hi,

Histogram plays asn important role in performance tuning. When we analyze a table/index oracle store the high and low value of each column of the table on the basis of this stats optimized choose the best way to operate. it is known as histogram. To create a histogram use ANALYZE TABLE COMPUTE STATISTICS FOR ALL COLUMNS SIZE 100;

This query divide the table into 100 different slices to create the histogram. AS more slices u give the more accurate value will be. This stats provide the accurate info abt the data values in columns of the table to optimizer. Optimizer will use it to perform operations on the table/indexex.

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Re: what is the advantage and disadvantage of a histogram? [message #62907 is a reply to message #59154]

Mon, 23 August 2004 16:58

Monica
Messages: 37
Registered: February 2000

Member

I need to know what is the advantage and disadvantage of a histogram?

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