title: SQL Server UNION - What is the default ORDER BY Behaviour
body: <p>If I have a few UNION Statements as a contrived example:</p>
  
  <pre><code>SELECT * FROM xxx WHERE z = 1
  UNION 
  SELECT * FROM xxx WHERE z = 2
  UNION
  SELECT * FROM xxx WHERE z = 3
  </code></pre>
  
  <p><strong>What is the default <code>order by</code> behaviour?</strong></p>
  
  <p>The test data I'm seeing essentially does not return the data in the order that is specified above. I.e. the data is ordered, but I wanted to know what are the rules of precedence on this.</p>
  
  <p>Another thing is that in this case xxx is a View.  The view joins 3 different tables together to return the results I want.</p>