I have a legacy database with which I need to interface. There are two tables that are joined together by two fields, and neither field is the primary key of its associated table. Is constructing an association between these tables beyond the capability of Rails? -- Posted via http://www.ruby-forum.com/.
Do these tables have primary keys? If so, they can be models just like anything else. You''ll just use find_by_sql to retrieve the data. If you are not able to represent them with ActiveRecord models, you always have the option of using straight DBI to connect to the database and retrieve data. believe it''s possible in Rails, just not as easy. On 8/2/06, James Reeves <jreeves@monkeyengines.co.uk> wrote:> > I have a legacy database with which I need to interface. There are two > tables that are joined together by two fields, and neither field is the > primary key of its associated table. Is constructing an association > between these tables beyond the capability of Rails? > > -- > Posted via http://www.ruby-forum.com/. > _______________________________________________ > Rails mailing list > Rails@lists.rubyonrails.org > http://lists.rubyonrails.org/mailman/listinfo/rails >-------------- next part -------------- An HTML attachment was scrubbed... URL: http://wrath.rubyonrails.org/pipermail/rails/attachments/20060802/303432e4/attachment.html
James/Brian
its possible in rails to use the DBI interface in 2 ways
1. using require ''dbi''; con =
DBI.connect("DBI::OCI8::your db
name............ #assuming its oracle
and then proceeding with prepared statement or adhoc sql execute on DB
handle
2. or accessing connection object from your model object and using execute
method to execute arbitary sql
i.e. yourModelInstance.connection.execute("your model related sql")
yourModelInstance can be accessed in any member function using
''self''
The only problem I faced while doing this was that there was no easy way of
populating my modelInstance with data retreived from call to execute, until
and unless I manually want to retreieve values from DBI::Row objects or
Cursor.fetch
Let me know how it goes.
-daya
On 8/2/06, Brian Hogan <bphogan@gmail.com> wrote:>
> Do these tables have primary keys? If so, they can be models just like
> anything else. You''ll just use find_by_sql to retrieve the data.
>
> If you are not able to represent them with ActiveRecord models, you always
> have the option of using straight DBI to connect to the database and
> retrieve data.
>
> believe it''s possible in Rails, just not as easy.
>
>
>
> On 8/2/06, James Reeves <jreeves@monkeyengines.co.uk > wrote:
> >
> > I have a legacy database with which I need to interface. There are two
> > tables that are joined together by two fields, and neither field is
the
> > primary key of its associated table. Is constructing an association
> > between these tables beyond the capability of Rails?
> >
> > --
> > Posted via http://www.ruby-forum.com/.
> > _______________________________________________
> > Rails mailing list
> > Rails@lists.rubyonrails.org
> > http://lists.rubyonrails.org/mailman/listinfo/rails
> >
>
>
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
http://wrath.rubyonrails.org/pipermail/rails/attachments/20060802/27db5364/attachment.html
James Reeves wrote:> I have a legacy database with which I need to interface. There are two > tables that are joined together by two fields, and neither field is the > primary key of its associated table. Is constructing an association > between these tables beyond the capability of Rails?You can use the :finder_sql option on associations to define how your aoosicated objects are retrieved. class Word has_many :sentences, :finder_sql => ''SELECT * FROM sentences WHERE body LIKE %#{self.word}%'' end -- Posted via http://www.ruby-forum.com/.
Alex Wayne wrote:> You can use the :finder_sql option on associations to define how your > aoosicated objects are retrieved.I note that Rails cannot infer joins from the SQL, however; it''s just a one-shot device. Is there a way of specifying a fragment of SQL such that I can take advantage of eager loading (via :include) in finds? Otherwise, I''m going to have an SQL statement fired off for every row in a rather large table! -- Posted via http://www.ruby-forum.com/.
Brian Hogan wrote:> Do these tables have primary keys? If so, they can be models just like > anything else. You''ll just use find_by_sql to retrieve the data.Fortunately, they do have primary keys (though their relationship is defined by other fields). Is it possible to retrieve an ActiveRecord and its associations via find_by_sql? -- Posted via http://www.ruby-forum.com/.
James: Maybe we''re over-thinking this: Would you be able to paste your migrations and your model''s associations so we could see tem and offer a better solution? You can email me off list if it''s confidential. On 8/3/06, James Reeves <jreeves@monkeyengines.co.uk> wrote:> > Brian Hogan wrote: > > Do these tables have primary keys? If so, they can be models just like > > anything else. You''ll just use find_by_sql to retrieve the data. > > Fortunately, they do have primary keys (though their relationship is > defined by other fields). Is it possible to retrieve an ActiveRecord and > its associations via find_by_sql? > > -- > Posted via http://www.ruby-forum.com/. > _______________________________________________ > Rails mailing list > Rails@lists.rubyonrails.org > http://lists.rubyonrails.org/mailman/listinfo/rails >-------------- next part -------------- An HTML attachment was scrubbed... URL: http://wrath.rubyonrails.org/pipermail/rails/attachments/20060804/ee0ee5b0/attachment.html