Help me create primary_key with ActiveRecord::Migration

I have two tables books and categories.
I create a join table books_categories.
Now how to create couple primary key(book_id,category_id)

class BooksCategories < ActiveRecord::Migration
  def self.up
     create_table :books_categories,:id => false do |t|
        t.integer :book_id
        t.integer :category_id
     end
  end
..............
end

Tuan Minh wrote:

I have two tables books and categories.
I create a join table books_categories.
Now how to create couple primary key(book_id,category_id)

class BooksCategories < ActiveRecord::Migration
  def self.up
     create_table :books_categories,:id => false do |t|
        t.integer :book_id
        t.integer :category_id
     end
  end
..............
end

I believe by default rails will create a primary key for you

You are removing your “primary key” with the :id => false

It’s not technically a “primary key” but by default ActiveRecord will look at that column.

Hope that helps some.

Bryan Ray wrote:

It's not technically a "primary key" but by default ActiveRecord will
look at that column.

Actually: