Sorry Suraci,
The concept is totally opposite. LINQ is intended to query application objects. There is nothing to deal with Database objects. To retrieve database object you still require T-SQL and Sql Stored Procedures.
Now if your application wants to filter the data result in application end when the user filters, you dont need to get the filtered data again from the database, rather you can use the existing data and easily filter the objects in the same way as you do in database. The capability of Grouping, Joining etc gives you an edge to filter critera in application end which would require lots of code if you do manually using normal loops.
Please take a look of my article on LINQ. I think examples might clear most of your doubts
http://www.codeproject.com/KB/dotnet/LINQ.asp[
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