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

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)

Added below contents,

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

and then, in my environment.rb file added below contents,

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

And it worked.