another simple SQL question

Ok here is another simple question from a novice....

Here is what my table looks like

firstname lastname fullname
---------- ---------- -----------
smith, john
green, susan
white, jeff

How can I break the fullname field into firstname lastname fields so it
looks like the following:

firstname lastname fullname
--------- --------- ---------
john smith smith, john
susan green green, susan
jeff white white, jeff

Please let me know. Sorry for such simple novice questions, I appreciate
your support.

THANKS!