title: Structuring db tables and rows for blog comments
body: <p>I am creating blog application, where all users can comment under posts.</p>
  
  <p>Blog has registered users who can comment and comment will appear with their name which defined in their profile, but guests should have ability to comment too, only difference that if user is not logged in I show 3 inputs for firstname, lastname and email, which are required to be filled.</p>
  
  <p>So in db I have tables <code>users</code> and <code>comments</code>. <code>comments</code> table has foreign key of <code>users</code> table, as well as 3 columns <code>firstname</code>, <code>lastname</code> and <code>email</code>.</p>
  
  <p>When user is logged and write comment, I am saving comment of user with users firstname, lastname and email from his/her account as well as users foreign key, but when he/she is guest I am saving his firstname, lastname and email horizontally in <code>comments</code> table.</p>
  
  <p>I want to know, should I save only foreign key? or it is not bad approach to save users firstname, lastname and email that already I have horizontally in comment alongside with id of user which's data I already have?</p>