Hi Friends,

SQL Server Filtered indexes use a filter predicate to index a portion of the table, a well-defined subset of data. They can be considered to be an optimized alternative to full-table indexes provided it is properly designed. Since filtered indexes will only index a subset of data, they require less storage, offer improved query performance while retrieving data from that subset of data and may/may not offer reduced maintenance overhead depending on how frequently that data is modified.

Here is a small example of using Filtered Indexes from BOL.