Question

I have a model where a place has some descriptions, those descriptions are associated with interests (place.description.interests). A user looking at the view for a place is represented in the model as a user, who also has a number of interests.

What I want to do is sort the description by overlapping interests (including zero overlapping), where my current Linq is:

place dest = (from p in _db.places
                          where p.short_name == id
                          select p).Single();

 return View(dest);

Now the following will do what I want in SQL on the schema in question:

SELECT COUNT(interest_user.user_id) AS matches, description.*
FROM description JOIN interest_description ON description.user_id = interest_description.user_id AND description.place_id = interest_description.place_id
    JOIN interest ON interest_description.interest_id = interest.interest_id
    LEFT JOIN interest_user ON interest.interest_id = interest_user.interest_id 
WHERE interest_user.user_id = 2
    AND description.place_id = 1
GROUP BY interest_description.user_id, interest_description.place_id
ORDER BY matches DESC

But I’m too new to Linq to know how I would handle this correctly. Ideally I could pull this off while still passing in a strongly typed model.

I have managed this so far:

var desc = from d in _db.descriptions
                       from i in d.interests
                       from u in i.users.DefaultIfEmpty()
                       where d.place_id == PlaceID
                           && (u.user_id == userID

(PlaceID and UserID are arguments passed to the controller that is managing this).

Simply put, given this linq, I just need to return d, ordered by a count of i.

my model

Answer 1

when your linq query becomes overly complex, i will suggest you creating views in your database and putting them on dbml designer. I have experienced at couple of situations when doing a lot of grouping in linq queries resulted in inefficient sql. Using views will not only result in straight forward linq queries but it also uses the sql that you want.