Question

I have a really strange problem.

I simply want to select all posts that feature in two given categories.

Heres my SQL:

SELECT  wp_posts.ID 
FROM wp_posts 
INNER JOIN wp_term_relationships ON wp_posts.ID = wp_term_relationships.object_id
WHERE  wp_term_relationships.term_taxonomy_id  = 83  
   AND   wp_term_relationships.term_taxonomy_id  = 84

This should return one result but it doesnt return anything.

If I comment out:

*wp_term_relationships.term_taxonomy_id  = 83* 

The post im looking for is returned.

If I comment out:

*wp_term_relationships.term_taxonomy_id  = 84*

Again, the post is returned.

Why then,when both of these conditions are included, nothing is returned?

Any help will be appreciated.Thanks

Answer 1

If you want to return all posts that have both those term_taxonomy_id‘s associated with them you can use:

SELECT  p.ID 
FROM wp_posts p
INNER JOIN wp_term_relationships r
  ON p.ID = r.object_id
WHERE  r.term_taxonomy_id IN (83, 84)
GROUP BY p.ID 
HAVING count(distinct r.term_taxonomy_id) =2

This will return all records that have both taxonomy terms.

Your query will not work because the term_taxonomy_id cannot have two values at the same time. You can change your query to use OR instead of AND or you can use the version I provided.