title: Difference between a normal ajax and long polling
body: <p>I'm trying to understand more about long polling to "manipulate" a website in real time, saw some videos and I'm thinking so far:</p>
  
  <p>Say I have an old date that the sql and I make an echo on it. As long polling will know if the old date will not be the same as it will look from time to time according to the setInterval function ...?</p>
  
  <p>Say I want to show publication of a blog in which all text is in mysql, but repende I publish a new publication, and who is on the page at the time, you will see the publication time (not tell me?), Then how one long polling code will know the difference between the old and the new publication? Ate even not to give conflicting or repeating the same date engraved on the sql.</p>