OK, I got the table creation piece, but I'm still not sure how to set up the
models. Here's what I have and what I'd like to work (changed key to tuning
because that was getting too confusing for an example) ...
<<
require 'rubygems'
require 'sequel'
DB = Sequel.sqlite
DB.create_table :books do
primary_key :id
column :title, :text, :unique=>true
end
DB.create_table :tunes do
primary_key :id
column :title, :text, :unique=>true
end
DB.create_table :tunings do
primary_key :id
column :tuning, :text, :unique=>true
end
DB.create_table :books_tunes_tunings do
primary_key :id
foreign_key :book_id, :books
foreign_key :tuning_id, :tunings
foreign_key :tune_id, :tunes
end
class Book < Sequel::Model
end
class Tune < Sequel::Model
end
class Tuning < Sequel::Model
end
book1 = Book.create(:title => 'Book 1')
book2 = Book.create(:title => 'Book 2')
tune1 = Tune.create(:title => 'Tune 1')
tune2 = Tune.create(:title => 'Tune 2')
tuning1 = Tuning.create(:tuning => 'C')
tuning2 = Tuning.create(:tuning => 'D')
book1.add_tune_tuning(tune1, tuning1)
book2.add_tune_tuning(tune2, tuning1)
# etc.
>>
I know in the say book model I'd need something like ...
many_to_many :???, :class => Tuning,
:join_table => :books_tunes_tunings, :left_key => :book_id,
:right_key => :tuning_id
but I'm not sure of what makes sense in the "???" part of if I have the
left/right key portion correct.
And ... ask long as I'm bothering everyone, how do I actually put
information in the join table? I'd also like to have a page number there (at
least that's where it makes sense to me). Is that the right way to do it?
How would I in the "add_tune_tuning" method also specify the page number?
Thanks again,
Scott
On Sat, Dec 11, 2010 at 8:59 PM, Scott LaBounty <[email protected]> wrote:
> Thanks for the quick help Jeremy. I'll give it a try.
>
> Scott
>
>
> On Sat, Dec 11, 2010 at 8:24 PM, Jeremy Evans <[email protected]>wrote:
>
>> On Dec 11, 7:46 pm, Scott LaBounty <[email protected]> wrote:
>> > All,
>> >
>> > I have three items, books, tunes, and keys. A book can have multiple
>> tunes,
>> > and a tune can appear in multiple books in different keys. I'm not quite
>> > sure how to express this either as database tables or models. If it were
>> > just say books and tunes, I'd have a join table between them and
>> > many_to_many relationships. I'm just not sure how to add in the third
>> piece.
>>
>> You want a three way join table:
>>
>> books_tunes_keys:
>> book_id references books
>> tune_id references tunes
>> key_id references keys
>>
>> You can use a standard Sequel many_to_many relationship, but you will
>> need to specify the :join_table=>:books_tunes_keys option.
>>
>> Jeremy
>>
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>
>
> --
> Scott
> http://steamcode.blogspot.com/
>
--
Scott
http://steamcode.blogspot.com/
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