为什么在sql server 2008中使用非聚集索引时增加估计的子树成本？

但是当在TimePeriodName列上定义非聚集索引时 Then Estimated subtree cost comes 0.0032886But when defined non clustered index on column TimePeriodNameCREATE UNIQUE NONCLUSTERED INDEX IX_TimePeriod_TimePeriodNameON TimePeriod( TimePeriodName ASC) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) 然后运行查询 Then run query SELECT * FROM TimePeriod where timeperiodname='quarter' 我得到估计子树成本是0.0065704 那么为什么非成本增加聚集索引是在表上定义的吗？ 我在做错误的地方e？I get Estimated subtree cost is 0.0065704So why is cost incresing when non clustered index is defined on the table?Where I am doing mistake?推荐答案 http://social.msdn.microsoft.com/Forums/en-US/transactsql/thread/c1d30080-db97-4b5b-a712-505eaf6d4836 [ ^ ] 希望它给出你的答案 数据库性能优化第1部分（索引策略） [ ^ ] 这将给出你对它有一个很好的解释..希望它会有所帮助.. http://social.msdn.microsoft.com/Forums/en-US/transactsql/thread/c1d30080-db97-4b5b-a712-505eaf6d4836[^]Hope its gives your answerDatabase performance optimization part 1 (Indexing strategies)[^]and this will give you a nice explanation on it..hope it will help.. 这篇关于为什么在sql server 2008中使用非聚集索引时增加估计的子树成本？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！