So in Rails 4 the long desired feature to use not queries has been added.
Article.where.not(title: \'Rails 3\')
Has similar su
Article.where(title: ['Rails 3', 'Rails 4'])
is how you'd do that in Active Record.
It's not possible to replicate any arbitrary SQL query using "Rails-y" syntax. But you can always just pass in literal sql.
So you could also do:
Article.where("articles.title = 'Rails 3' OR articles.title = 'Rails 4'")