with Ajax you can achieve what ever you do with a normal language
you can view, add ,update and delete.
depending on the platform you are using, you can find the Ajax dlls thats working with it.
for example in case of asp.net just go to this site
http://www.asp.net/ajax and download what you need with ajax
in your case PHP check this
http://ajaxpatterns.org/PHP_Ajax_Frameworksof if you want interactive javascript
http://www.dojotoolkit.org/http://jquery.com/http://freeajaxscripts.net/you have got lots of resources on the internet for ajax with lots of examples.