SQL Server group queries the entire data for a maximum value (including LINQ notation)

To achieve the following effect, is the most time after grouping the data:

1. SQL

        Select  *        from    (select    *,                            row_number () through (PARTITION by Rip_guid ORDER by Ru_createdtime DESC) RN                  from      Rip_flowinfo                ) T        WHERE   t.rn <= 1;  

2. LINQ

    var groupquery = from T in query Group T by T.rip_guid to G select new {key = G.key, Source = g.orderbydescending (TT =& Gt Tt.ru_createdtime). FirstOrDefault ()};

　　

SQL Server group queries the entire data for a maximum value (including LINQ notation)