Though this article uses the Adventure Works database for its examples, I’ve decided to create an example table for use within the database to help better illustrate the examples. The SQL UPDATE statement is used to change column values.
Though an update statement can modify columns data from many sources, such as literal values or other query results, the basic format is the same.
In the Find & Replace dialog box you can use Regex if necessary (in the “Use” drop down list, select “Regular Expression”, 2008 and R2). Using XMLA alter command In SSMS Object Explorer, navigate to the measure group containing the partitions then script as Alter. Do a “Replace all” to replace “Table1” with “Table2” and execute the XMLA.
In the previous example of a 1 million row table, there is no longer the need to update 200,000 rows to update the statistics on the table if trace flag 2371 is activated.
In SQL Server 2016, you don't need to turn on trace flag 2371 because this new method is used by default by the SQL Server engine when determining when to update the statistics.
Statistics are small objects that describe the data distribution for tables and indexes in a SQL Server database.
These statistics are used by the SQL Server Query Optimizer to determine the best plan to execute a query.
The downside is that the threshold is very high for tables with a large number of rows which leads to updates occurring less frequently which can cause performance issues.
In order to trigger the auto update statistics feature in SQL Server, the number of updated rows should exceed 20% of the table rows.In this way the statistics will be updated more frequently and will guarantee better query performance.Say you have a Measure Group with 100 partitions with source SQL = “select [some columns] from table1 where col1 = X” where X = 1 to 100. The statistics that start with _WA means that it is automatically created using the AUTO_CREATE_STATISTICS feature: The DBCC Show_Statistics command can be used to show the statistics details, such as the updated date and the number of rows in the table.To use, you just need to specify the table name and statistic name as follows: As previously mentioned, to trigger the auto update statistics feature, more than 20% of the table rows should be updated.In this article we’ll explore how to use the UPDATE statement.