EnumStatistics Method

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The EnumStatistics method returns a QueryResults object that enumerates index statistics used to support Microsoft SQL Server query optimization.

語法

object
.EnumStatistics( )
as 
QueryResults

Parts

• object
  Expression that evaluates to an object in the Applies To list.

Prototype (C/C++)

HRESULT EnumStatistics(
LPSQLDMOQUERYRESULTS* ppResults);

Returns

A QueryResults object that contains three result sets. The first result set describes index statistics structure and age and is defined by these columns.

Column	Data type	Description
Average key length	real	Average length of an index row.
Density	real	Selectivity of the index.
Rows	integer	Number of rows in the table.
Rows Sampled	integer	Number of rows sampled for statistics data.
Steps	integer	Number of distribution steps.
Updated	nvarchar(21)	Date and time of most recent update.

The second result set describes index density and is defined by these columns.

Column	Data type	Description
All density	real	Selectivity of the column(s) listed in Columns.
Columns	nvarchar(129)	Column(s) participating in index.

The third result set enumerates histogram values and is defined by these columns.

Column	Data type	Description
Steps	nvarchar(6)	Histogram values in the current distribution statistics.

備註

Statistics are calculated for an index when the index is first used in query optimization or at user direction. Statistics are updated automatically at configurable intervals. When statistics have not been calculated on an index, the EnumStatistics method succeeds but returns no result sets.

Applies To:

Index Object