title: What's the best to check if item exist or not: Select Count(ID)OR Exist(...)?
body: <p>What's the best in performance to determined if an item exist or not specially if the table contain more than 700,000 row  </p>
  
  <pre><code>if (Select count(id) from Registeration where email='email@w.cn') &gt; 0
      print 'Exist'
  else
      print 'Not Exist'
  </code></pre>
  
  <p>OR</p>
  
  <pre><code>if Exists(Select id from Registeration where email='email@w.cn') 
      print 'Exist'
  else
      print 'Not Exist'
  </code></pre>