title: Merge columns with empty values in oracle
body: <p>I have two columns of data <code>name1</code> and <code>name2</code>. I need to merge these columns but they are arranged like this:</p>
  <pre><code>name1 | name2
  1       empty
  empty   2
  3       empty
  empty   4
  </code></pre>
  <p>Here empty means a blank space in the table.</p>
  <p>I need the output to be like this</p>
  <pre><code>1
  2
  3
  4
  </code></pre>