Making a custom single-category page

I want to make a page that is hard-coded to display the last few posts in a particular category, but I’m having trouble working out what the sql query should be. I had worked it out to this:
SELECT DISTINCT * FROM $tableposts WHERE (category_id = 8) ORDER BY post_date LIMIT 8
..but it complains that category_id is an unknown column. What would the correct query be?