title: select level from dual connect by level<=4 how it works internally
body: <p>I know level usage along with hierarchical queries but I am not able to understand how to analyze this:</p>
  
  <pre><code>(select level from dual connect by level&lt;=4) 
  </code></pre>
  
  <p>query works internally and how it is generating numbers.</p>
  
  <p>For generating numbers I had another way that is:</p>
  
  <pre><code>select r from (select rownum r from all_objects) e where r&lt;=10 
  </code></pre>
  
  <p>it will generate the first 10 numbers. But I am not able to understand how level is working internally. </p>
  
  <p>Please explain why!</p>