http://msdn.microsoft.com/zh-cn/library/ms177484.aspx
SQLServer索引的四个高级特性
http://blog.youkuaiyun.com/yzsind/article/details/8719594
http://msdn.microsoft.com/zh-cn/library/ms177484.aspx
http://blog.youkuaiyun.com/yzsind/article/details/8719594