title: Get cartesian product of two columns
body: <p>How can I get the cartesian product of two columns in one table?</p>
  
  <p>I have table</p>
  
  <pre><code>A    1
  A    2
  B    3
  B    4
  </code></pre>
  
  <p>and I want a new table</p>
  
  <pre><code>A    1
  A    2
  A    3
  A    4
  B    1
  B    2
  B    3
  B    4
  </code></pre>