1030 - Got error 28 from storage engine

( SELECT article_name, article_table, article_uid, portfolioid, A.idx, ad.yyyybegins AS StartYear, ad.yyyyends as EndYear, CONCAT(p.forenames, ' ', p.surname) AS Author, CONCAT(COALESCE(p.surname, ''), '', COALESCE(p.forenames, ''), ' ', article_name) AS sorter FROM portfolio_articles A LEFT JOIN works W ON A.article_uid = W.UID2 LEFT JOIN people p ON W.authoruid = p.UID LEFT JOIN article_dates ad ON ad.ArticleId = W.UID2 AND ad.ArticleTypeId = 3 AND id_article_date_index_type = 4 WHERE article_table = 'works' AND portfolioid = 2467 ) UNION ALL ( SELECT article_name, article_table, article_uid, portfolioid, idx, ad.yyyybegins AS Begins4, ad.yyyyends AS Ends4, 'N/A', article_name AS sorter FROM portfolio_articles A LEFT JOIN topicsa T ON A.article_uid = T.UID4 LEFT JOIN article_dates ad ON ad.ArticleId = T.UID4 AND ad.ArticleTypeId = 2 AND ad.id_article_date_index_type = 3 WHERE article_table = 'topics' AND portfolioid = 2467 ) UNION ALL ( SELECT article_name, article_table, article_uid, portfolioid, A.idx, ad.yyyybegins AS firstact, ad.yyyyends AS lastact, 'N/A', CONCAT(COALESCE(P.surname, ''), '', COALESCE(P.forenames, ''), ' ', article_name) AS sorter FROM portfolio_articles A LEFT JOIN people P ON A.article_uid = P.UID LEFT JOIN article_dates ad ON P.UID = ad.ArticleId AND ad.ArticleTypeId = 1 AND id_article_date_index_type = 2 WHERE article_table = 'people' AND portfolioid = 2467 ) ORDER by sorter ASC