title: How to add commas every 3 digits character for string in Microsoft Server SQL?
body: <p>Is there a built-in function for this task? If not, how can it be done? It is <code>varchar(20)</code>, and it only contains integers. For example, <code>309000 -&gt; 309,000</code>.</p>
  
  <p>Any idea?  </p>
  
  <p>Thanks,  </p>