title: What is the fastest way to query for NULL values in SQL Server?
body: <p>I am trying to find all records which contain NULLs in a column. The column is indexed. However, when when I set my <code>where</code> clause to </p>
  
  <pre><code>where person_key is null
  </code></pre>
  
  <p>SQL Server takes a really long time to respond. Queries looking for specific values, on the other hand, return quite quickly.</p>
  
  <p>Is there a way to write the query to speed up the the search for records with  NULLs in person_key?</p>