title: insert a NOT NULL column to an existing table
body: <p>I have tried:</p>
  
  <pre><code>ALTER TABLE MY_TABLE 
  ADD STAGE INT NOT NULL;
  </code></pre>
  
  <p>But it gives this error message:</p>
  
  <blockquote>
    <p>ALTER TABLE only allows columns to be added that can contain nulls or
    have a DEFAULT definition specified</p>
  </blockquote>