about: Select tables optimized away

When I explain SELECT MAX(o_id)-1 FROM orders,it tell me Select tables optimized away.What is it meaning?It show me good or bad? thanks! _ 与联机的朋友进行交流，请使用 MSN Messenger: http://messenger.msn.com/cn -- MySQL General

Re: about: Select tables optimized away

Hello. Similar questions were asked in the list before. For example see: http://lists.mysql.com/mysql/41542 Search in archives at: http://lists.mysql.com/mysql From sources I've found that this message appears when optimizing queries with count(*), min() and max(). The above