EnumStatistics Method
Questa funzionalità verrà rimossa in una delle prossime versioni di Microsoft SQL Server. Evitare di utilizzare questa funzionalità in un nuovo progetto di sviluppo e prevedere interventi di modifica nelle applicazioni in cui è attualmente implementata.
The EnumStatistics method returns a QueryResults object that enumerates index statistics used to support Microsoft SQL Server query optimization.
Sintassi
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. |
Osservazioni
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.