Sql server updating large databases

Posted by / 27-Jan-2017 15:29

Typically, the default sampling ratio is enough to generate good execution plans. For example, my colleagues and I once had a large table with approximately 12 million records in the table.

The number of records in the table was fairly static.

are metadata about the data within a table and they're created and updated on a column-by-column basis, not on the entire table.

The database engine employs statistics when generating execution plans that are used to access data stored within the database.

The prefered method for updating SQL Server statistics is the UPDATE STATISTICS command.

This command allows much greater flexibility when programming, however it does require more initial programming.

When you fine-tune UPDATE STATISTICS to perform within your environment, you will find that it is time well spent.

When fine-tuning the UPDATE STATISTICS command, you can choose from several options.

Statistics are automatically updated when certain thresholds within SQL Server are met, i.e., the number of rows in the table increases or decreases by 10% of the number of rows the statistic was based on.The massive number of queries would send SQL Server's CPU to 100% utilization.We decided to start updating the statistics using the FULLSCAN flag.Manually updating statistics There are two ways to manually update statistics on a table.One is via the sp_updatestats system stored procedure. While the sp_updatestats procedure is an easier way to program the command, the UPDATE STATISTICS command is much more flexible and much more powerful.

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Once the threshold is reached, SQL Server will automatically update the statistic(s) defined in the table.