Radio Buttons and MySQL PHP

Hello, my problem is this: I have a mysql table, and the form has a group
radio buttons. I want a certain field in the table to be updated, depending on
which of the radio buttons is selected. For example, if Radio button A is
selected then I want Field A in the database to be set to 1, if Radio button B
is selected then I want Field B in the table to be set to 1. Your help is much
appreciated, thank you.