So - today I've been made this question.
"I have a DB, AUTO_UPDATE_STATISTICS option OFF (very bad idea, anyway :-)), I rebuild my indexes every week. I do not have major changes in my database. As update statistics with fullscan is a side effect of DBCC DBREINDEX (aka INDEX REBUILD in 2005), can I say all my statistics are fine and up to date?"
Well... No :-(
In fact, statistics created from DBCC DBREINDEX (aka INDEX REBUILD in 2005) are only statistics over indexed columns. Statistics over non-indexed column (the ones named something like _WA_sys) are not managed from these operations. Therefore, if you want these to be up to date you need to turn AUTO_UPDATE_SATTISTICS ON or to schedule their management in other way.
More info can be found at:
Is statistics over non-indexed columns updated by index rebuild?
- Beatrice Nicolini -