title: Why is there a SELECT 1 from table?
body: <p>I came across a fictitious SQL, i am not sure what is the original intend, it looks like:</p>
  
  <pre><code>SELECT COUNT (*)
  INTO miss
  FROM billing b
  WHERE b.network= network1 
  and NOT EXISTS (SELECT 1 from vas NV WHERE NV.network =  
  b.network);
  </code></pre>
  
  <p>Why is there a select 1, and not exists?</p>