ActiveRecord query for related elements

I have a Solutions model, with has_many Reviews, and Reviews with 'has_many' ReviewValues. Each ReviewValue is also linked to a Tag which contains the tag name. I'm trying to select the avarage scores (for all the Tags so grouped by tag) that go with a particular solution.

Basically the Reviews model is the join table between Solutions and ReviewValues (and there's also the Tags table which contains the names)

What I have so far is this:

@total =

The problem is that I can only call review_values on one specific review and not for all of them. so I'd have to do something like doesn't help me because I need the average for each reviewvalue (by Tag name)

This is what the review_values table looks like:

Table review_values
id, tag_id, review_id, score, created_at, updated_at
id               int(11) PK
tag_id           int(11)
review_id        int(11)
score            int(11)
created_at       datetime
updated_at       datetime

And the tags table:

Table tags
id, name
id               int(11) PK
name             varchar(255)


Have you tried using :through ? eg:

class Solution
    has_many :reviews
    has_many :review_values, :through => :reviews

@total = my_solution.review_values.average(:score)

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