Multiple aggregates in linq to entities (code first) - entity-framework

Question

Given the following model, I want to be able to retrieve the number of points gained for a single player and the average number of point gained for all players given a time period. This should be done in a single db query (I also want other stats e.g. avg points per team which will come later but the concept should be the same).
Having a bad day and getting nowhere. Can someone help me out?
public class Player
{
public int Id { get; set; }
public ICollection<PlayerGame> PlayerGames { get; set; }
...
}
public class PlayerGame
{
public int Id { get; set; }
public int Points { get; set; }
public int PlayerId { get; set; }
public Player Player { get; set; }
public int GameId { get; set; }
public Game Game { get; set; }
...
}
public class Game
{
public int Id { get; set; }
...
}
Edit:
OK. Have taken the game entity out of the equation for now and changed your code to fit in with my repo. This is what I have now:
var query = from p in _playerRepository.Query()
from pg in p.PlayerGames
group new { p, pg } by 1 into ppg
select new
{
SinglePlayerPointsGained = (from x in ppg
where x.p.Id == playerId && x.pg.Date > startDateTime
select x.pg.Points).Sum(),
AveragePoints = (from x in ppg
where x.pg.Date > startDateTime
select x.pg.Points).Average(),
};
So Now I just need the AveragePoints calculation to take players that have not played in the period into account as mentioned in the comment.

Answer 1

I assumed the Game class had a DateTime property. The basic idea is using the group by 1 trick
DateTime startDateTime, endDateTime;
int playerId;
var query = from p in context.Players
join pg in context.Players on p.Id equals pg.PlayerId
join g in context.Games on pg.GameId equals g.Id
group new { p, pg, g } by 1 into ppgg
select new {
SinglePlayerPointsGained = (from x in ppgg
where x.p.PlayerId == playerId
where x.g.DateTime >= startDateTime && x.g.DateTime <= endDateTime
select x.pg.Points ).Sum(),
AveragePoints = (from x in ppgg
group x.pg.Points by x.p.PlayerId into g
select g.Key).Average()
};