Rails - Nov 2007 - Computed Columns?

Time to stretch.

I want to acheive a find that returns a computed value as a column.  I
don''t know SQL (thanks to Rails hiding me from it up until now) and I
don''t know if Rails will be able to help.  Here''s my model.

class Trackable < ActiveRecord::Base
   has_many :time_entries, :dependent => :destroy
   has_many :time_chargers, :through => :time_entries, :source
=> :owner, :uniq => true
end

# Of course I can do:

trackables = Trackable.find(:all)

# Now assume that    trackables[0].time_chargers
# would return 3 people:  Fred Flinstone, Wilma Flinstone, Barny
Rubble
# I can then get how many time_chargers there are by doing:

trackables[0].time_chargers.size   # => 3

# I want that value computed by the original SQL query returned from
find, so additional queries aren''t created.
# Further I want to be able to do the same search with conditions
added to time_chargers at the time of the find.

# Something like:

trackables = Trackable.find :all,  with_scope =>
"time_chargers.last_name == Flinstone"

# So now I get:

trackables[0].time_chargers.size   # => 2

# again without an additional SQL query.

I suppose if I have to dive down to SQL that''s ok, but mixing Rails
generated SQL and hand crafted SQL feels so wrong.  That''s and I
don''t
really know SQL.  Where should I begin?

Ryan
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Hi,

if your tables are not really huge I think you can just add
an :include option to your first find(:all) for your associations...
which means that rails will load table data for the assocations as
well in that one query.


--
Volker

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---