Rails - Jan 2007 - Sum multiple columns individually

Can you sum a few columns at a time?

I tried
x =Calc.find(:all, :select => "sum(amt1) amt1, sum(amt2) amt2"
:conditions => ["where date > ?", date] )

The sql seems to function properly, but I wasn''t able to grab the
values.  These  just failed

x.amt1
x.send("amt1")

I tried changing up the query to use

sum(amt1) as amt1
sum(amt1) ''amt1''
sum(amt1) as ''amt1''

but none worked.

undefined method `amt1'' for [#<;Calc:0x2ac605ec9508
@attributes={"amt1"=>2.0, "amt2"=>2.0}>}>]:Array

the "amt"=> 2 are correct, but I just cant seem to access the value

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On 1/25/07, Alex Treber
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
>
> Can you sum a few columns at a time?
>
> I tried
> x =Calc.find(:all, :select => "sum(amt1) amt1, sum(amt2) amt2"
> :conditions => ["where date > ?", date] )
>
> The sql seems to function properly, but I wasn''t able to grab the
> values.  These  just failed
>
> x.amt1
> x.send("amt1")
You''re getting back an array.  Try x[0].amt1 for example.

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JDL wrote:
> You''re getting back an array.  Try x[0].amt1 for example.
That did it.  I thought it was a little odd that I had to do
x[0].amt2 as well, but I suppose the array is the first thing returned 
then I''m going after each element.

Thanks for the help!

Alex

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On 1/25/07, Alex Treber
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
>
> JDL wrote:
> > You''re getting back an array.  Try x[0].amt1 for example.
>
> That did it.  I thought it was a little odd that I had to do
> x[0].amt2 as well, but I suppose the array is the first thing returned
> then I''m going after each element.
>
> Thanks for the help!
Using find(:first) or find(:all) is incorrect here since technically
you''re not retrieving a model.  You''re retrieving aggregated
data from
the db.  It''d be nice to add support for multiple values to
ActiveRecord::Calculations, but I can''t envision a decent API that
doesn''t look hackish.  Your best bet is to use connection.select_all
or select_values

# returns array of values, like [1, 5]
def sum_amounts
  connection.select_values("SELECT sum(amt1), sum(amt2) ...")
end

or..

# select_all returns an array, but since it''s an aggregation, it
should only return 1 row.
# Calling #first returns a hash like { ''amt1'' => 1,
''amt2'' => 5 }
def sum_amounts
  connection.select_all("SELECT sum(amt1), sum(amt2) ...").first
end
-- 
Rick Olson
http://weblog.techno-weenie.net
http://mephistoblog.com

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