I'm not sure exactly what your asking but here is a couple thoughts.
<input type='radio' name='a' value='whatever' <? if ($row['a'] == 'y') { echo "checked"; } ?>>
^ That would tell it on or off ^
<input type='radio' name='a' value='<?=$row['a']?>'>
^ Would give the button a value from the db ^
Is that what you where looking for?
-Cy