title: Delete rows using case when condition in SQL Server
body: <p>Say I write this query</p>
  
  <pre><code>select
      x1, x2, x3 act
  from 
      mytab
  </code></pre>
  
  <p>I need delete rows using any condition</p>
  
  <pre><code>case when x1=b, and act=0, then delete these rows
  </code></pre>
  
  <p>At the same time, i need to delete rows that contain a <code>null</code> value by <code>x1</code> column.</p>
  
  <p>How can I do that?</p>