The following is reference material, and not required reading. For a deeper understanding however it is recommended. For some topics, multiple links have been provided to give different explainations and viewpoints on the topics.
- http://api.rubyonrails.org/classes/ActiveRecord/Migration.html
- http://en.wikibooks.org/wiki/Ruby_on_Rails/ActiveRecord/Migrations
- http://en.wikibooks.org/wiki/Ruby_on_Rails/ActiveRecord/Validations
- http://api.rubyonrails.org/classes/ActiveModel/Validator.html
- http://edgeguides.rubyonrails.org/active_record_validations.html
- http://railscasts.com/episodes/211-validations-in-rails-3