Joining queries with Entity Framework - linq

Question

I have the table
MOVIES_RATING:
MovieID int
MovieRating decimal
I'd like to get 2 values using one query:
select COUNT(*)
FROM [dbo].[MOVIES_RATING]
where [dbo].[MOVIES_RATING].[MovieID] = 78
and
select SUM([dbo].[MOVIES_RATING].Rating)
FROM [dbo].[MOVIES_RATING]
where [dbo].[MOVIES_RATING].[MovieID] = 78
That's what I got in LINQ:
(from p in ef.MOVIES_RATING.Where(r => r.MovieID== movie_id)
let movieRates = ef.MOVIES_RATING.Where(r => r.MovieID == movie_id)
let count = movieRates.Count()
let averageUserRating = movieRates.Sum(c => c.MOVIES_RATING)/count
select new MovieRating {AverageUserRating = averageUserRating, VoteCount = count})
.Take(1);
Looks awful as well as SQL being generated:
SELECT
[Limit1].[MovieID] AS [MovieID],
[Limit1].[C2] AS [C1],
[Limit1].[C1] AS [C2]
FROM ( SELECT TOP 1
[GroupBy1].[A1] AS [C1],
[Extent1].[MovieID] AS [MovieID],
[GroupBy2].[A1] / CAST( [GroupBy1].[A1] AS decimal(19,0)) AS [C2]
FROM [dbo].[MOVIES_RATING] AS [Extent1]
CROSS JOIN (SELECT
COUNT(1) AS [A1]
FROM [dbo].[MOVIES_RATING] AS [Extent2]
WHERE [Extent2].[MovieID] = 78 ) AS [GroupBy1]
CROSS JOIN (SELECT
SUM([Extent3].[Rating]) AS [A1]
FROM [dbo].[MOVIES_RATING] AS [Extent3]
WHERE [Extent3].[MovieID] = 78 ) AS [GroupBy2]
WHERE [Extent1].[MovieID] = 78
) AS [Limit1]
I'm not sure it is best solution, so any help is appreciated.
I know It can be done using stored procedure, but if its could be done using LINQ it would be better.

Answer 1

from r in ef.MOVIES_RATING
group r by r.MovieID into g
where g.Key == movie_id
select new
{
Count = g.Count(),
Sum = g.Sum(r => r.Rating)
}
(or perhaps filter first then group; it probably translates to the same SQL anyway)
Another approach, using Aggregate:
ef.MOVIES_RATING
.Where(r => r.MovieID == movie_id)
.Aggregate(
new { Count = 0, Sum = 0 },
(acc, r) => new { Count = acc.Count + 1, Sum = acc.Sum + r.Rating });
(not sure how it translates to SQL though)

Answer 2

What about simple query:
var query = from m in context.Movies
where m.Id == 78
select new
{
Count = m.MovieRatings.Count(),
Sum = m.MovieRatings.Sum(mr => mr.Rating)
};
var data = query.SingleOrDefault();
Moving average computation to your application code should reduce the SQL query complexity.