Truncate table updating statistics Meet girls for sex totally free

In this example, we will use the Adventure Works database, the Person. The table contains 19,614 rows and we will insert additional 10,000 records. After updating table statistics, the correct values are shown. The All density value is calculated as 1/total number of distinct rows.

truncate table updating statistics-7

In this article, we will show how to update SQL Server statistics, what are the updating costs, and when updating is recommended.

The statistics shown by this command are created using the default sampling rate.

Even if the obsolete statistics are used, there will be almost no performance degradation.

However, this is valid only for tables with a small number of records.

In the example above, we showed how time-consuming updating statistics can be for a large number of table rows, and how the SAMPLE parameter can help.

The next question is whether you should use the default SQL Server sampling rate, or specify your custom sampling rate using the SAMPLE parameter.

Another method to update statistics is to use the sp_updatestats stored procedure, but this is recommended only for advanced users, as the procedure updates statistics for all tables and indexed views in the database, which can significantly downgrade SQL Server performance. Although the statistics are inaccurate, the estimated query execution plan shows the correct number of records.

If there were no data changes on the table, UPDATE STATISTICS will have no effect. On a table with frequent data changes, statistics old an hour can be obsolete and inaccurate. However, this is the case only for the tables with a small number of records, such as this one.

This behavior provides accurate statistics for small tables, as updating statistics for small tables cost is less than the inaccurate statistics cost.

When SQL Server statistics on large tables are updated with the SAMPLE parameter, sampling percent isn’t ignored, and the number of sampled rows in lower than the number of table rows.

Address table before the records were added, when the table had 19,614 rows. The number of the sampled rows is slightly higher than 10% of the total row number.

Tags: , ,