You can start with small small programs from w3school web site. http://www.w3schools.com/ajax/default.asp

And then try to write your ajax code with Jquery.
Because you have to write less code for ajax, if you are using jquery.

if you know the jquery you can use the below code

$(document).ready(function() {
$('#div_id').load('/abc.jsp');

});

Hello Sir,,U can use java script for that on load of your welcome page call a java script function and from that call another jsp page which consist the code for database connection and also fetch required details for you and the redirect that jsp to welcome page and then u can show ur data on welcome page

its core AJAX call

Are you using some Client side framework like dojo,extJS etc or it is a core AJAX call?