title: Performance problems after updating statistics SQL Server 2014
body: <p>I've received a database that was previously on SQL Server 2008R2 but was just put on a SQL Server 2014 instance. There were no maintenance tasks run of any kind run on the database since 2014 (e.g. Rebuilding of indexes, updating statistics, etc.).  </p>
  
  <p>Once we ran update statistics as part of our regularly scheduled maintenance that we do on a set schedule, the performance of some queries has taken a massive hit to the point where some select statements will seem to never finish.  </p>
  
  <p>The queries have some <code>CASE...WHEN</code> statements in them, but I wouldn't expect there to be such a performance hit.  Does anybody have any thoughts on what might cause such issues?</p>
  
  <p>I've tried updating the compatibility level to 120 since it was on 100 when the database first came in but, that didn't make any difference on the performance.</p>