I need to retreive a list of posts that have (at least) one attachment that belongs to a category in WordPress.

The relation between attachments and categories I made by myself using the WordPress default method.

Here's the query that i'm running right now:

SELECT p.*
FROM `wp_posts` AS p # The post
    INNER JOIN `wp_posts` AS a # The attachment
        ON p.`ID` = a.`post_parent`
        AND a.`post_type` = 'attachment'
    INNER JOIN `wp_term_relationships` AS ra
        ON a.`ID` = ra.`object_id`
        AND ra.`term_taxonomy_id` IN (3) # The category ID list
WHERE p.`post_type` = 'post'
ORDER BY p.`post_date` DESC
LIMIT 15

The problem here is that the query only use the first found attachment, and if it doesn't belongs to the category, the result isn't returned.