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Double sql join query

Double sql join query

Getting WordPress features images (_thumbnail_id) that have an empty caption and return the ID’s and there relative path (_wp_attachment_file).

SELECT POST.ID, POST.TITLE, POST.EXCERPT, META.VALUE FROM
(SELECT p.ID AS ID, p.post_title AS TITLE, p.post_type, p.post_excerpt AS EXCERPT FROM wpka_posts AS p
INNER JOIN wpka_postmeta AS pm
ON pm.meta_value = p.ID
AND pm.meta_key = '_thumbnail_id'
AND p.post_parent != 0
AND p.post_type = 'attachment'
AND p.post_excerpt = ''
LIMIT 20) AS POST
JOIN (
    SELECT pa.meta_value AS VALUE, pa.meta_key, pa.post_id AS ID FROM wpka_postmeta AS pa
     WHERE pa.meta_key = '_wp_attached_file') AS META
ON POST.ID = META.ID;