Updating index statistics sql
2) By default, the UPDATE STATISTICS statement uses only a sample of records of the table.Using UPDATE STATISTICS WITH FULLSCAN will scan the entire table.In general you should consider the following important points, focusing in the fact that there are two kinds of statistics: index and column statistics.1) By default, the UPDATE STATISTICS statement updates both index and column statistics.Before you go ahead and state the fact that you have AUTO_UPDATE_STATISTICS ON for your databases remember that does not mean that they are being updated! Here is a simple block of code that will iterate through all your databases in order to build the sp_updatestats command that can then be copied and pasted into a new query window for execution.This code will work with all current and previous versions of SQL Server back through SQL 7.0.That is why so many of us "roll our own" index maintenance solutions as it were. Ah, at any rate, by only maintaining indexes that are fragmented, statistics updates do not occur globally against the tables/indexes in your databases. I've touched upon this in an earlier tip, SQL Server's engine will update the statistic when: Based upon this criteria, there will be many cases where the underlying data changes in such a way or in such levels that the statistics that exist for an index will not be indicative of the actual data in the database.
That is whether such actions are required or not for a specific index, a rebuild of the index and all the locking and churning in the logs occurs.
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.
Once the threshold is reached, SQL Server will automatically update the statistic(s) defined in the table.
On my test server this code yields the following results.
The next step is to copy this text, paste it into a query window in SQL Server Management Studio, then execute it against the instance.