During normal execution of queries, DML statements, and LOAD TABLE statements, the database server automatically maintains
column statistics for use by the optimizer. The benefit of maintaining statistics for some columns may not outweigh the overhead
necessary to generate them. For example, if a column is not queried often, or if it is subject to periodic mass changes that
are eventually rolled back, there is little value in continually updating its statistics. Use the ALTER STATISTICS statement
to suppress the automatic updating of statistics for these types of columns.
When automatic updating is disabled, you can still update the statistics for the column using the CREATE STATISTICS and DROP
STATISTICS statements. However, you should only update them if it has been determined that it would have a positive impact
on performance. Normally, column statistics should not be disabled.
If automatic updating has been disabled, the statistics may become out of date. Re-enabling does not immediately bring them
up to date. Execute the CREATE STATISTICS statement to recreate them, if necessary.