title: generating model with ActiveRecord associations
body: <p>Folks,</p>
  
  <p>I am working on creating an application where I have two entities in my problem space. One entity is "biologist" and the other entity is "experiment" now one biologist can have many experiments and each experiment can have many biologist.</p>
  
  <p>I know how to create models and routes using the command line generator:</p>
  
  <pre><code> rails generate scaffold Biologist name:string expertise:string last_pub:text
  </code></pre>
  
  <p>What is the right way to add an association? Is it to go and update the model code after generation? What is unclear to me is if I add a "belongs_to" association post generation how does that reflect in the DB schema without running a migration or something? In the above example if "experiment" belongs to "biologist" then there will be a foreign key in the "biologist" table, how will that be created if I add the associations in the model class post generation. I am fairly new to rails, so I apologize if this is a naive question.</p>