Dies ist die letzte Antwort, die für mich funktioniert hat.
SELECT DISTINCT
post_title
, post_content
,(SELECT meta_value FROM wp_postmeta WHERE wp_postmeta.meta_key = 'Asking Price (US\$)' AND wp_postmeta.post_id = wp_posts.ID) AS "Asking Price (US\$)"
,(SELECT group_concat(wp_terms.name separator ', ')
FROM wp_terms
INNER JOIN wp_term_taxonomy on wp_terms.term_id = wp_term_taxonomy.term_id
INNER JOIN wp_term_relationships wpr on wpr.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id
WHERE taxonomy= 'category' and wp_posts.ID = wpr.object_id
) AS "Categories"
,(SELECT group_concat(wp_terms.name separator ', ')
FROM wp_terms
INNER JOIN wp_term_taxonomy on wp_terms.term_id = wp_term_taxonomy.term_id
INNER JOIN wp_term_relationships wpr on wpr.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id
WHERE taxonomy= 'post_tag' and wp_posts.ID = wpr.object_id
) AS "Tags"
FROM wp_posts
WHERE post_type = 'post'
ORDER BY
post_title
, post_content
