Mysql2::Error: All parts of a PRIMARY KEY must be NOT NULL; if you need NULL in a key, use UNIQUE instead

Question

I have created a demo application in rails 3.2.9 and ruby versiion 2.0.0 . After scaffolding Blog model I am trying to migrate it, but having following issue.

# rake db:migrate

== CreateBlogs: migrating ====================================================

-- create_table(:blogs) rake aborted!

StandardError: An error has occurred, all later migrations canceled:

Mysql2::Error: All parts of a PRIMARY KEY must be NOT NULL; if you need NULL in a key, use UNIQUE instead: CREATE TABLE blogs (id int(11) DEFAULT NULL auto_increment PRIMARY KEY, title varchar(255), description text, created_at datetime NOT NULL, updated_at datetime NOT NULL) ENGINE=InnoDB /usr/local/rvm/gems/ruby-2.0.0-p648@demo-app/gems/activerecord-3.2.9/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:245:in query' /usr/local/rvm/gems/ruby-2.0.0-p648@demo-app/gems/activerecord-3.2.9/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:245:inblock in execute' /usr/local/rvm/gems/ruby-2.0.0-p648@demo-app/gems/activerecord-

....

....

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-3.2.9/lib/active_record/migration.rb:551:in migrate' /usr/local/rvm/gems/ruby-2.0.0-p648@demo-app/gems/activerecord-3.2.9/lib/active_record/railties/databases.rake:179:inblock (2 levels) in ' /usr/local/rvm/gems/ruby-2.0.0-p648@demo-app/gems/rake-11.3.0/exe/rake:27:in `' Tasks: TOP => db:migrate (See full trace by running task with --trace)

Answer 1

I had this problem too (mysql 0.3.21 and Rails 3.2.22.5). I fixed it by adding a file in my application config/initializers/mysql2_adapter.rb (as there was no such file before) with the below content:

require 'active_record/connection_adapters/mysql2_adapter'
class ActiveRecord::ConnectionAdapters::Mysql2Adapter
  NATIVE_DATABASE_TYPES[:primary_key] = "int(11) auto_increment PRIMARY KEY"
end

Then, in my environment.rb file, I've added below content:

require File.expand_path('../initializers/mysql2_adapter', __FILE__)