Oracle statistics invalidating sql
The problem is that, in certain cases, SQL Server’s automatic statistics maintenance may update the statistics too infrequently, or not provide the optimizer enough information to define properly the data distribution.
This is when the DBA may need to step in and manage statistics manually.
Database backups, integrity checks, and performance optimizations form the core of a DBA’s regular maintenance tasks.
Backups are usually at the top of the list, as data is one of the most important, if not most important, facets of a business.
In previous releases, statistics gathered for global temporary tables (GTTs) were common to all sessions.
If you knew the GTTs would need vastly different statistics for each session, you could avoid statistics and rely on dynamic sampling to provide the relevant information.
Integrity checks are also essential as database corruption must be found and corrected as quickly as possible, to mitigate downtime and data loss.
Second, assuming the database option is enabled, which it is by default, SQL Server will create single-column statistics whenever a column, which is not already the leading column in an existing index, is used in a query predicate (e.g.
in the search condition of a command ( to create single- and multi-column statistics manually.
In a multi-column statistic, whether index or column-level, the histogram only exists for the first column (they are “left-based”).
For example, if the index is on ( is not the leading column in another existing index).