SQL Query to retrieve posts by category

Hi, being new to WordPress, can someone please help me with a query I need to retrieve posts belonging to a specifc category or categories as supplied by an argument from a widget …

This is the code I have currently, where $includecats is the categories to include and $show is the number of posts to list..

$posts = $wpdb->get_results(“SELECT DISTINCT * FROM $wpdb->posts
INNER JOIN $wpdb->term_relationships ON $wpdb->posts.ID = $wpdb->term_relationships.object_id
INNER JOIN $wpdb->term_taxonomy
ON $wpdb->term_relationships.term_taxonomy_id = $wpdb->term_taxonomy.term_taxonomy_id
WHERE $wpdb->term_taxonomy.term_id = ‘$includecats’ AND post_type=’post’ AND post_date < NOW( ) AND post_status = ‘publish’ ORDER BY post_date DESC LIMIT $show”);

The result I get is two posts duplicated and one posts that has is not categorised under the category I am trying to retrieve but has a tag in the post.

Any help will be highly appreciated. Thx