Question

I have the following table:

And the following data:

How can i filter the result, so that i only get the latest row from each omraade_id (sorted descending by timestamp)?

Which in this case would be the rows with id: 1010 and 1005

—

From @lazyberezovsky’s answer, i have created the following expression:

dbConnection = new ElecEntities();

            var query = from data in dbConnection.Valgdata
            orderby data.timestamp descending
            group data by data.omraade_id into g
            select g.FirstOrDefault();

            return query.ToList();

It returns two rows with the ID 3 and 4, which are the first two rows in the database, and also the ones with the lowest timestamp. Any idea why?

Answer 1

I have no experience with EF, so I’m unsure if only SQL-esque linq works here. A plain C#-ish:

var query = dbConnection.Valgdata.GroupBy(u => u.omraade_id)
      .Select(x => x.FirstOrDefault(y => x.Max(p => p.timestamp) == y.timestamp));