How to find all posts without category and assign the "Uncategorized"?

Question

Hi is there anybody who can help me how to find all posts without category and assign the "Uncategorized"? I have more than 7000 posts and 300 of them are without category, how I could assing one?

And another question, how I can assign category to all posts (except bulk edit which doesnt work well with this amount of posts)?

Answer 1

The current accepted takes posts out of range too. Since it LEFT JOIN on wp_term_relationships without knowing that the first join might be a Category or a Post_tag, it gives false-positive, hence affecting posts that might not be without category.

Inspired from the current accepted answer, change the "37" for your actual wanted category:

INSERT IGNORE INTO wp_term_relationships
(object_id, term_taxonomy_id, term_order)
SELECT p.ID as `object_id`, 37 as `term_taxonomy_id`, 0 as `term_order`
    FROM wp_posts p 
    WHERE p.post_type="post" 
        AND p.post_status='publish'
        AND NOT EXISTS
        (
        SELECT  *
        FROM    wp_term_relationships rel
        JOIN    wp_term_taxonomy tax
        ON      tax.term_taxonomy_id = rel.term_taxonomy_id 
                AND tax.taxonomy = 'category' 
        JOIN    wp_terms term
        ON      term.term_id = tax.term_id
        WHERE   p.ID = rel.object_id 
        )

Answer 2

You can do it through sql query. Add your category id instead 37.

INSERT IGNORE INTO wp_term_relationships
(object_id, term_taxonomy_id, term_order)
SELECT 
    wp_posts.ID as object_id,
    37 as term_taxonomy_id,
    0 as term_order
FROM    wp_posts
LEFT JOIN 
        wp_term_relationships rel
ON      wp_posts.ID = rel.object_id 
LEFT JOIN 
        wp_term_taxonomy tax
ON      tax.term_taxonomy_id = rel.term_taxonomy_id 
        AND tax.taxonomy = 'category' 
LEFT JOIN 
        wp_terms term
ON      term.term_id = tax.term_id
WHERE   wp_posts.post_type = 'post' 
        AND wp_posts.post_status = 'publish' 
        AND term.term_id is null

Answer 3

If you don't set any category to your post then it'll automatically be assigned to Uncategorized. You don't need to assign it manually to Uncategorized

And for assigning category to bulk posts you can use wp_set_post_categories() function. Get all of your posts(which you need to assign category) in an array and run a loop theough the array with wp_set_post_categories( $post_ID, $post_categories, $append ) passing needed parameter. It will assign the category to your posts.