Rails - Mar 2005 - Newbie question: Rails as a solution for existing databases

Hello,

I seem to be getting the picture that Rails is great for situations in which
the developer is able to specify the database schema/structure.

Is it just as good at being used on existing database schemas that have not
been designed to be "Rails friendly"?

Or does Rails have limitations and expectations of the database schema that
makes it impratical to apply to existing databases?

Please forgive me if it is an obvious question - I am yet a newbie with
Rails.

Cheers

Andrew Stuart

I''m not an expert on ActiveRecord, but I can speak from my experience
thus far.  If your existing databases follow basic relational
principles, eg foreign keys, join tables, normalized data, then it
shouldn''t be too difficult to define Models on top of them. 
It''s
always possible in ActiveRecord to specify the foriegn key name and
table name for relationships and definitions.  I''ve had good luck with
this type of thing, at least.

-dave


On Sat, 19 Mar 2005 09:43:41 +1100, Andrew Stuart
<andrew.stuart-HYVr4Vs6GMsQrrorzV6ljw@public.gmane.org>
wrote:
> Hello,
> 
> I seem to be getting the picture that Rails is great for situations in
which
> the developer is able to specify the database schema/structure.
> 
> Is it just as good at being used on existing database schemas that have not
> been designed to be "Rails friendly"?
> 
> Or does Rails have limitations and expectations of the database schema that
> makes it impratical to apply to existing databases?
> 
> Please forgive me if it is an obvious question - I am yet a newbie with
> Rails.
> 
> Cheers
> 
> Andrew Stuart
> 
> _______________________________________________
> Rails mailing list
> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>

David Adams wrote:
> I''m not an expert on ActiveRecord, but I can speak from my
experience
> thus far.  If your existing databases follow basic relational
> principles, eg foreign keys, join tables, normalized data, then it
> shouldn''t be too difficult to define Models on top of them.
What about databases that don''t use auto-incrementing integers for keys
(for situtations where a natural primary key already exists, and so on) 
?  I wasn''t able to find much in the documentation about that.

Thanks,
   Kevin

Kevin McConnell wrote:
> What about databases that don''t use auto-incrementing integers for
keys
> (for situtations where a natural primary key already exists, and so on) 
> ?  I wasn''t able to find much in the documentation about that.
Whoops - went looking again and it turned out to be really simple. 
Posting this folow up just in case it''s helpful to the OP.

You can specify the primary_key name with (duh) self.primary_key, as in:

   class Report < ActiveRecord::Base
     def self.table_name() ''report''; end
     def self.primary_key() ''report_id'' end
   end

But be aware that its value will use the accessor "id", not
"report_id":

   r = Report.new()
   r.id = 123

Cheers
   Kevin