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EnumStatistics Method

未來的 Microsoft SQL Server 版本將移除這項功能。請避免在新的開發工作中使用這項功能,並規劃修改目前使用這項功能的應用程式。

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: