title: ISNULL vs IS NULL in SQL Server
body: <p>I have question related to <code>isnull()</code> function vs <code>is null</code> keyword in SQL Server.</p>
  
  <p>I know that writing below condition in where clause of SQL statement will result in bad performance </p>
  
  <pre><code>isnull(@C_FirstName, '') &lt;&gt; ''
  </code></pre>
  
  <p>We can  replace same with  </p>
  
  <pre><code> (@C_FirstName IS NOT NULL AND @C_FirstName &lt;&gt; '') 
  </code></pre>
  
  <p>in the <code>where</code> clause</p>
  
  <p>But will I get any performance gain in case of if condition? </p>
  
  <p>Below is the example with two option</p>
  
  <p>Option #1:</p>
  
  <pre><code>If `isnull(@C_FirstName, '') &lt;&gt; ''`  
  </code></pre>
  
  <p>Option #2:</p>
  
  <pre><code>If `(@C_FirstName IS NOT NULL AND @C_FirstName &lt;&gt; '')`
  </code></pre>
  
  <p>From option 1 and option 2 which statement is recommended?</p>