Constraints for grouping

I have a question that I've thought in my head about using triggers, but
I figure to ask people that do SQL more than I. So, I have a table that
I want two columns.

(1) A featured column which is for only 1 row, once it switched to
another row than all other rows must be false

title | author_id | categories | featured
--------------------------------+-----------+------+-----
Thierry Beta Release | 3 | 11 | True
Different Approach | 3 | 11 |
Ottawa Does Not Heart Hip-Hop | 3 | 11 |

(2) A featured column by category and only allow category_feature equal
to the number of categories.

Is SQL the way to go (and how - ideas), or should I use python for the
heavy lifting?

Thanks for any input,
J