Hi @jamilj ,
I had the same error message and I could to resolv with this code belong:
CREATE TEMPORARY TABLE IF NOT EXISTS authors2delete AS (
SELECT author_id
FROM authors
WHERE publication_id IS NULL
);
DELETE FROM author_settings WHERE author_id IN ( SELECT author_id FROM authors2delete );
DELETE FROM books_for_review_authors WHERE author_id IN ( SELECT author_id FROM authors2delete );
DELETE FROM submission_comments WHERE author_id IN ( SELECT author_id FROM authors2delete );
DELETE FROM authors WHERE author_id IN ( SELECT author_id FROM authors2delete );
DROP TABLE authors2delete;
Try it.