Consider the following code books = Book.limit(10) books.each do |book| puts book.author.last_name end In the above code, a query is made each time the lastname of an author of a book is needed in puts book.author.last_name. A single query for each book.

Suppose you're making a book tracking app to keep a log of all the books you consume. And you want to log the format. As in, was it an ebook, an audiobook or was it an actual physical paper copy? You would create a column named format on your model.

Rails console is useful playground for trying out various view helper commands as well as experimenting with our Active Record data model. Here is a rundown of some of the things we can do with in a Rails console session. Basic commands Reloading the Console We can enter the Rails

What are polymorphic associations? When do we need to create join tables? When do we use single table inheritence? We will cover some more advanced topics with Active Record Associations in this post. Note: This post assumes that you are already familiar with common Active Record associations. You can see

In Rails, an association is a connection between two Active Record models. With associations we get convenient utility methods to easily query and do operations on those models. Rails has the following associations belongs_to, has_many, has_one, has_one :through, has_many :through, has_and_belongs_to_many