Add a Tag to each Post in a Category
A WP user had a large number of posts in a certain category. They wanted to add a tag to each post in that category. Here is the procedure to do that with SQL commands.
1. Create the new tag.
2. Get the new tag’s term_taxonomy_id (assume it is 4 for this example)
3. Get the category’s term_taxonomy_id (assume it is 55 for this example)
4. Create a table from all rows in wp_term_relationships where
the term_taxonomy_id is 55.
CREATE TABLE temp
SELECT * FROM wp_term_relationships
WHERE term_taxonomy_id = 55
5. Insert a term_relationships row for each row in the temp table.
INSERT IGNORE INTO wp_term_relationships
SELECT temp.object_id, 4, 0
LEFT JOIN wp_posts p ON (p.ID = temp.object_id)
WHERE p.post_type = ‘post’
AND p.post_status = ‘publish’