title: Check whether a column is empty
body: <p>I need to retrieve columns of a row that one of its data types is empty.
  Extra VARCHAR
  Extra has nothing in it </p>
  
  <p>Show those with empty extra column </p>
  
  <pre><code>  Select * FROM Items WHERE Extra ?????
  </code></pre>
  
  <p>What should be the condition ?</p>