title: SQL: What does NULL as ColumnName imply
body: <p>I understand that <code>AS</code> is used to create an alias. Therefore, it makes sense to have one long name aliased as a shorter one. However, I am seeing a <code>SQL</code> query <code>NULL as ColumnName</code>
  What does this imply?</p>
  
  <pre><code>SELECT *, NULL as aColumn
  </code></pre>