Get posts with no tags assigned to them

HI,

I modified your title a little as the original one didn’t make much sense ??

The following will get any post without a tag, it’s specifically tuned towards posts and tags, but can also be adjusted to deal with pages (or any CPT, or just all content altogether) as well as categories instead of terms.

global $wpdb;

$entries = $wpdb->get_results( $wpdb->prepare( "
	SELECT
		p.ID,
		t.term_id
	FROM
		" . $wpdb->posts . " p
	LEFT JOIN
		(
			SELECT
				term_rel.object_id,
				term_rel.term_taxonomy_id,
				t.taxonomy,
				t.term_id
			FROM
				" . $wpdb->term_relationships . " term_rel
			JOIN
				" . $wpdb->term_taxonomy . " t
					ON ( t.term_taxonomy_id = term_rel.term_taxonomy_id )
			WHERE
				t.taxonomy = %s
			GROUP BY
				term_rel.object_id
		) t
		ON ( t.object_id = p.ID )
	WHERE
		t.term_id IS NULL
	AND
		p.post_type = %s
", 'post_tag', 'post' ) );

What I did here is to just pull the ID number of the posts, but I only include posts where the term_id is NULL (empty).

I check the term_id value by running a sub-query which grabs any post_tag entry and group them based on post ID (referenced as object_id by the database) and then I only pull out the row that has an object_id that matches our current post id (the ON ( t.object_id = p.ID ) block)