Start Updating a table from another table in sql server

Updating a table from another table in sql server

There are a few reasons that a DBA might choose to manually manage the maintenance of statistics: 1.

Automatic statistic maintenance: There are three database scoped options that directly impact statistic maintenance: auto_create, auto_update and auto_update_async.

Auto create dictates whether the query optimiser will create statistics on columns used in predicates during optimisation if required.

If the transaction is attempted again – the statistics are still stale, and an update is initiated…

Using the auto update async option should ameliorate this issue by spawning the update onto a background thread while the original query proceeds with the stale stats. The threshold at which a statistic is declared stale for tables greater than 500 rows is 500 20% of total rows. Highly skewed updates can cause statistics to become misleading long before this threshold is reached.

A statistic object is automatically created for every index on a table, and if the auto_create_statistics database option is set then the optimiser will create a statistic object for every column in a query predicate.

A statistics object can also be created with the CREATE STATISTICS ddl.

Statistics can be examined at a database level by querying the system view sys.stats.