I have run the Database Tuning Advisor and it has suggested that some statistics are created. Whilst this is great and I understand the purpose of statistics, when I have reviewed them it has created 5 or more with very similar columns included in them. If I went ahead and created these statistics, if a column is replicated in more than one of these statistics and the first statistic is updated, how does this update affect the other statistics?
Thanks,
Best Answer
Including multiple columns in statistics adds a new dimension that cannot be estimated otherwise: correlation.
Query Predicate Contains Multiple Correlated Columns
Optimizing Queries That Access Correlated datetime Columns
All statistic need to be updated to be accurate.
Whether all stats recommended by the DTA are necessary, that is a different topic.