http://api.rubyonrails.org/classes/ActiveRecord/AttributeMethods/PrimaryKey/ClassMethods.html#method-i-set_primary_key http://api.rubyonrails.org/classes/Active

http://api.rubyonrails.org/classes/ActiveRecord/AttributeMethods/PrimaryKey/ClassMethods.html#method-i-set_primary_key http://api.rubyonrails.org/classes/ActiveRecord/AttributeMet... http://guides.rubyonrails.org/migrations.html#writing-a-migration http://guides.rubyonrails.org/migrations.html#writing-a-migr...