How to check if a post belongs to a category in Wordpress

Question

I need to check if a certain post is belongs to a category or belongs to a descendant of a certain category. IS there a wordpress function for this, or I need to do it myself ?

Edit: I should have mentioned that the WP version is 2.7. sorry

Answer 1

$post = get_post($id);
$category = $post->$post_category;
cat_is_ancestor_of(($parent_category, $category));

For more info see the get_post and cat is ancestor of references. Also, while somewhat difficult to find this is a good place to start for most wp development related things.

Answer 2

Would the sql query work with wordpress 2.8?

Answer 3

See also here: http://codex.wordpress.org/Function_Reference/in_category#Testing_if_a_post_is_in_a_descendant_category

Answer 4

for 2.7 or above use in_category( $category, $_post )

Regards, Vicky Biswas