title: MySQL IFNULL "N/A" yields "item cannot be found in the collection" Error
body: <p>I have been using IFNULL functions to convert NULL values to zeros in my SQL queries, like this:</p>
  
  <pre><code>SELECT IFNULL(mem.comment_count,0) FROM members...
  </code></pre>
  
  <p>This works fine. I am now trying to use the IFNULL function to convert NULL values to a string, "N/A", but I keep getting the error: "item cannot be found in the collection corresponding to requested name or ordinal":</p>
  
  <pre><code>SELECT IFNULL(mem.address2,'N/A') FROM members...
  </code></pre>
  
  <p>I even tried using COALESCE just incase it's an empty string instead of a NULL:</p>
  
  <pre><code>SELECT COALESCE(NULLIF(mem.address2, ''), 'N/A') FROM members...
  </code></pre>
  
  <p>But still throws the same error.</p>
  
  <p>Any ideas?</p>