title: How to represent a many-to-many relationship in a relational database?
body: <p>I have two tables Country and Region. A Region is a set of one or several Countries. Some Countries are in no Region.</p>
  
  <p>How should I represent this in a relational database? I thought of the two following possibilities:</p>
  
  <ul>
  <li>Country has a Edition column that includes either null or the Edition that it belongs to. My problem with this: I have been taught nulls are evil in a database.</li>
  <li>Edition has a Countries column that is an array of Country. My problem with this: I have been taught arrays are evil in a database.</li>
  </ul>
  
  <p>What's the best practice?</p>