SELECT wp_posts.ID FROM wp_posts
LEFT JOIN wp_term_relationships ON
(wp_posts.ID = wp_term_relationships.object_id)
LEFT JOIN wp_term_taxonomy ON
(wp_term_relationships.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id)
WHERE wp_posts.post_status = 'publish'
AND wp_term_taxonomy.taxonomy = 'category'
AND wp_term_taxonomy.term_id = 42
AND datediff(CURDATE(), wp_posts.post_date) > 8