Re: Analyze all indexed columns

From: A. Bardeen <abardeen1_at_yahoo.com>
Date: Mon, 03 Sep 2001 06:00:15 -0700
Message-ID: <F001.00380DBB.20010903051042@fatcity.com>

Iain,

This is covered in greater detail in the SQL Reference manual under the Analyze command, but here's a summary of the basics.

Computing/estimating statistics on the table (without a FOR clause) calculates/estimates stats for the table and its indexes.

The for clause has the following options:   For Table - table stats only

  For Columns <column_list>
  All Columns
  For All Indexed Columns - gathers column stats on the specified columns, all columns, or only the indexed columns. If the SIZE option is also included, then histogram information is gathered as well.

For more details on histograms see metalink note 1031826.6 "Histograms: An Overview"

Some key details to consider before using histograms:

• they are not used with bind variables.
• they are useful only if the data is heavily skewed (i.e. it's not uniformly distributed)

HTH,

• Anita
  • "Nicoll, Iain (Calanais)" <iain.nicoll_at_calanais.com> wrote:
    > Apologies for what is probably a really simple
    > question but what is the
    > default behaviour of
    >
    > analyze table table_name compute statistics
    >
    > and would
    >
    > analyze table table_name compute statistics for
    > table for indexed columns
    > for all indexes
    >
    > be any better/worse than analyzing separately
    >
    > eg
    >
    > analyze table table_name compute statistics
    > analyze table table_name compute statistics for all
    > indexed columns
    > analyze index index_name compute statistics
    >
    > Version is Oracle 7.3. The only references I've got
    > access to don't appear
    > to make it clear.
    >
    > TIA
    >
    > Iain Nicoll
    

    ---

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Received on Mon Sep 03 2001 - 08:00:15 CDT