Subquery returns more than 1 row with a Wordpress postmeta query

Question

I am trying to pull data from a subsite's posts and postmeta tables:

SELECT xyz_8_posts.ID,

(select xyz_8_postmeta.meta_value
from xyz_8_postmeta
inner join xyz_8_posts
on xyz_8_postmeta.post_id = xyz_8_posts.ID
where xyz_8_postmeta.meta_key = 'presentation_title'
AND xyz_8_postmeta.post_id = xyz_8_posts.ID
) as 'Presentation Title'


FROM xyz_8_posts
WHERE xyz_8_posts.post_type = "presenters"

I'm getting a "Subquery returns more than 1 row" error. I don't understand why this is. If I replace xyz_8_posts.ID in the WHERE clause with an actual ID the query returns one title.

Firstly the inner join seems redundant and another thing is that there can be some posts who have multiple entries in meta table for meta key presentation_title — M Khalid Junaid, Jan 18 '21 at 19:20

score 2 · Accepted Answer · answered Jan 18 '21 at 19:18

You have an extra JOIN where you just want a correlated subquery:

SELECT p.ID,
      (select pm.meta_value
       from xyz_8_postmeta pm
       where pm.post_id = p.ID and
             pm.meta_key = 'presentation_title'
      ) as Presentation_Title
FROM xyz_8_posts p
WHERE p.post_type = 'presenters'

Subquery returns more than 1 row with a Wordpress postmeta query

1 Answers1