Lets just use your Magazine / Subscriber example for now.
I want to do something like this:
--------------------------------------------------------
class Magazine
def subscriber_salaries
Subscriber.calculate(:sum, :salary, :conditions => "magazine_id =
" + id.to_s) # PGError: ERROR: column "magazine_id" does not
exist
end
end
--------------------------------------------------------
But of course there is no "magazine_id" in the subscribers table
anymore because we've switched away from "subscriber has many
subscriptions".
Like you said, I'm guessing I should probably use a "find" like so:
some_model = Subscriber.find( ??? )
some_model. Subscriber.calculate(:sum, :salary)
But i don't know how to do that quite yet. (what goes in the ???)
Ideas?
On Sep 21, 12:40 pm, Dan Manges <[EMAIL PROTECTED]> wrote:
> Hi Dave,
>
> Can you post more of your code? If you're going through the
> association proxies, the calculation should work. Is 'table1' in your
> example a target of a has_many :through association? So do you have it
> set up something like this?
>
> class SomeModel < ActiveRecord::Base
> has_many :table1, :through => :something
> end
>
> some_model = SomeModel.find(:first)
> some_model.table1.sum(:enrich_bead_count_hemo)
>
> If you're just doing Table1.sum(:enrich_bead_count_hemo), (note the
> capitalized Table1), then it would be for all the rows, not just the
> associated ones.
>
> -Dan Mangeshttp://www.dcmanges.com/blog
>
> On Sep 21, 2:05 pm, dschruth <[EMAIL PROTECTED]> wrote:
>
> > Thanks for the response,
>
> > However, I tired what you suggested but only got to the same point as
> > before.
>
> > Both of these ways:
>
> > table1.calculate(:sum, :enrich_bead_count_hemo,
> > OR
> > table1.sum(:enrich_bead_count_hemo
>
> > give me the same answer: at total of *all* the rows in the other
> > table. But I want a sum of *just* the *associated* rows.
>
> > I was able to do this when the tables where directly related (with
> > a :condition statement). But I don't quite know how to do that yet
> > for HABTM or "has many :foo => :through"
>
> > Dave
>
> > On Sep 20, 9:53 pm, Dan Manges <[EMAIL PROTECTED]> wrote:
>
> > > You should take advantage of the association proxies. Something like
> > > this should work.
>
> > > class Magazine
> > > has_many :subscriptions
> > > has_many :subscribers, :through => :subscriptions
> > > end
>
> > > class Subscription
> > > belongs_to :magazine
> > > belongs_to :subscriber
> > > end
>
> > > class Subscriber
> > > has_many :subscriptions
> > > end
>
> > > Now you can do calculations like this:
>
> > > class Magazine
> > > def youngest_subscriber_birthday
> > > subscribers.calculate(:max, :date_of_birth)
> > > end
> > > end
>
> > > You should be able to do the calculation the same way for your
> > > 'enrich_bead_count_hemo'.
>
> > > -Dan Mangeshttp://www.dcmanges.com/blog
>
> > > On Sep 20, 10:06 pm, dschruth <[EMAIL PROTECTED]> wrote:
>
> > > > Hi,
>
> > > > I'm trying to sum up the records in a related table that used to just
> > > > be a child table. This line used to work:
>
> > > > table1.sum(:enrich_bead_count_hemo, :conditions => "table2_id = " +
> > > > id.to_s)
>
> > > > now I've got an intermediate "has and belongs to many" = HABTM table
> > > > inbetween them. Could somebody help me figure out how to sum across
> > > > two tables? I'm thinking i might have to use the custom SQL "join"
> > > > attribute of the sum method.
>
> > > > Thanks,
>
> > > > Dave
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