SELECT to_seconds(now()) - to_seconds(lastaccess) as seconds
FROM survey WHERE id=@param

var i = _db.Database.FromSql<int>(
    @"SELECT to_seconds(now()) - to_seconds(lastaccess) as seconds
      FROM survey WHERE id=@param;",
    @param).ToList();

entity.Property(e =>e.LastAccessComputed)
    .HasComputedColumnSql("to_seconds(now()) - to_seconds(lastaccess)");

var conn = _context.Database.GetDbConnection();
    try
    {
        await conn.OpenAsync();
        using (var command = conn.CreateCommand())
        {
            string query = "SELECT EnrollmentDate, COUNT(*) AS StudentCount "
                + "FROM Person "
                + "WHERE Discriminator = 'Student' "
                + "GROUP BY EnrollmentDate";
            command.CommandText = query;
            DbDataReader reader = await command.ExecuteReaderAsync();

            if (reader.HasRows)
            {
                while (await reader.ReadAsync())
                {
                    var row = new EnrollmentDateGroup { EnrollmentDate = reader.GetDateTime(0), StudentCount = reader.GetInt32(1) };
                    groups.Add(row);
                }
            }
            reader.Dispose();
        }
    }
    finally
    {
        conn.Close();
    }