Ajax does not insert anything, it is merely the medium which carries the data. The use of AJAX is to replace the older form submit so that you can carry out seamless actions in background.
Your receiving script which would live on the server would responsible for returning any control codes to indicate success or not.
Any problems with inserting data would be down to how good you are at programming for that eventuality.
Please remember to wrap any code you have in forum tags:-
[CODE]...[/CODE] [HTML]...[/HTML] [PHP]...[/PHP]
If you can't think outside the box, you will be trapped forever with no escape...