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Christian Johansen

2008-Oct-14 22:26 UTC

Has and belongs to many, join table id included in query

I''m using a habtm association for the first time and I''m
having some
trouble when inserting several rows. The id of the join table seems to
be set to an already existing id causing the insert to fail.

class ClassA < ActiveRecord::Base
  has_and_belongs_to_many :bs,
                          :class_name => "ClassB",
                          :join_table => :abs

end

class ClassB < ActiveRecord::Base
  belongs_to :class_a
end

My join table migration:

  def self.up
    create_table :abs do |t|
      t.integer :class_a_id, :null => false
      t.integer :class_b_id, :null => false
    end

    add_index :abs, [:class_a_id, :class_b_id], :unique => true
  end

Then finally in the controller:

@a.bs = ClassB.find params[:bs]
@a.save

Now, this works the first time, but the second time I get this back:

Mysql::Error: #23000Duplicate entry ''1'' for key 1: INSERT INTO
`abs`
(`class_a_id`, `id`, `class_b_id`) VALUES (7, 1, 1)

Now, I wonder - why is the id included in the query with a value that is
already used? I''m sure it''s just something I''m doing
wrong, but I''m
having a hard time figuring out what. I looked at the :insert_sql option
to habtm too, but don''t know how to include the ids dynamically?
-- 
Posted via http://www.ruby-forum.com/.

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Frederick Cheung

2008-Oct-14 22:47 UTC

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Re: Has and belongs to many, join table id included in query

On Oct 14, 11:26 pm, Christian Johansen <rails-mailing-l...@andreas-
s.net> wrote:> I''m using a habtm association for the first time and I''m
having some
> trouble when inserting several rows. The id of the join table seems to
> be set to an already existing id causing the insert to fail.
>habtm join tables should not have an id column (use :id => false as an
option to create_table)

Fred> class ClassA < ActiveRecord::Base
>   has_and_belongs_to_many :bs,
>                           :class_name => "ClassB",
>                           :join_table => :abs
>
> end
>
> class ClassB < ActiveRecord::Base
>   belongs_to :class_a
> end
>
> My join table migration:
>
>   def self.up
>     create_table :abs do |t|
>       t.integer :class_a_id, :null => false
>       t.integer :class_b_id, :null => false
>     end
>
>     add_index :abs, [:class_a_id, :class_b_id], :unique => true
>   end
>
> Then finally in the controller:
>
> @a.bs = ClassB.find params[:bs]
> @a.save
>
> Now, this works the first time, but the second time I get this back:
>
> Mysql::Error: #23000Duplicate entry ''1'' for key 1: INSERT
INTO `abs`
> (`class_a_id`, `id`, `class_b_id`) VALUES (7, 1, 1)
>
> Now, I wonder - why is the id included in the query with a value that is
> already used? I''m sure it''s just something I''m
doing wrong, but I''m
> having a hard time figuring out what. I looked at the :insert_sql option
> to habtm too, but don''t know how to include the ids dynamically?
> --
> Posted viahttp://www.ruby-forum.com/.--~--~---------~--~----~------------~-------~--~----~
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Bill Kocik

2008-Oct-14 23:52 UTC

head link

Re: Has and belongs to many, join table id included in query

Not to pimp my blog or anything, but I wrote about this exact issue
here: http://bkocik.net/2007/07/26/habtm-and-the-id-field/

That should help you understand what''s going on (in a very long-winded
manner). :)

On Oct 14, 6:26 pm, Christian Johansen <rails-mailing-l...@andreas-
s.net> wrote:> I''m using a habtm association for the first time and I''m
having some
> trouble when inserting several rows. The id of the join table seems to
> be set to an already existing id causing the insert to fail.
>
> class ClassA < ActiveRecord::Base
>   has_and_belongs_to_many :bs,
>                           :class_name => "ClassB",
>                           :join_table => :abs
>
> end
>
> class ClassB < ActiveRecord::Base
>   belongs_to :class_a
> end
>
> My join table migration:
>
>   def self.up
>     create_table :abs do |t|
>       t.integer :class_a_id, :null => false
>       t.integer :class_b_id, :null => false
>     end
>
>     add_index :abs, [:class_a_id, :class_b_id], :unique => true
>   end
>
> Then finally in the controller:
>
> @a.bs = ClassB.find params[:bs]
> @a.save
>
> Now, this works the first time, but the second time I get this back:
>
> Mysql::Error: #23000Duplicate entry ''1'' for key 1: INSERT
INTO `abs`
> (`class_a_id`, `id`, `class_b_id`) VALUES (7, 1, 1)
>
> Now, I wonder - why is the id included in the query with a value that is
> already used? I''m sure it''s just something I''m
doing wrong, but I''m
> having a hard time figuring out what. I looked at the :insert_sql option
> to habtm too, but don''t know how to include the ids dynamically?
> --
> Posted viahttp://www.ruby-forum.com/.--~--~---------~--~----~------------~-------~--~----~
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Christian Johansen

2008-Oct-15 09:15 UTC

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Re: Has and belongs to many, join table id included in query

Bill Kocik wrote:> Not to pimp my blog or anything, but I wrote about this exact issue
> here: http://bkocik.net/2007/07/26/habtm-and-the-id-field/
> 
> That should help you understand what''s going on (in a very
long-winded
> manner). :)
> 
> On Oct 14, 6:26�pm, Christian Johansen <rails-mailing-l...@andreas-
Ah, great stuff, thanks!
-- 
Posted via http://www.ruby-forum.com/.

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Rails - Oct 2008 - Has and belongs to many, join table id included in query

Has and belongs to many, join table id included in query

Re: Has and belongs to many, join table id included in query

Re: Has and belongs to many, join table id included in query

Re: Has and belongs to many, join table id included in query