SQL coalesce with empty string ,NULLIF is not usable in my system
<p>Try to use coalesce in my query, for example I want the following query</p>

<pre><code>COALESCE('', '','THIS')
</code></pre>

<p>give <code>'THIS'</code>, but it turns out to be  <code>''</code></p>

<p>Found one solution <a href="https://stackoverflow.com/questions/17283978/sql-coalesce-with-empty-string">SQL Coalesce with empty string</a>, but my system  could not accept NULLIF.</p>