links to read

Return type of list

 Generally, LINQ to Objects, LINQ to XML, LINQ to DataSets, and all that works on in-memory CLR objects return IEnumerable<T>.   For LINQ to SQL, LINQ to Entities which work on Expression Trees to generate SQL commands, the return type is IQueryable<T>.  

More references:http://blogs.msdn.com/wriju/archive/2008/05/06/linq-ienumerable-t-and-iqueryable-t.aspx
http://jonkruger.com/blog/2007/10/19/iqueryable-vs-ienumerable-in-linq-to-sql-queries/

http://www.codeproject.com/Articles/231163/IQueryable-Vs-IEnumerable-in-terms-of-LINQ-to-SQL 

View in SQL
http://www.codeproject.com/Articles/38560/Overview-of-View-in-SQL-Server-2005

http://msdn.microsoft.com/en-us/library/aa214068%28v=sql.80%29.aspx

used Defined Functions Limiatations/
Difference between userdefined functions and stored procedure