Cannot execute query [SELECT o.id AS id,
o.tiposcheda AS type,
o.titolo AS title,
o.titoloperord AS ordered_title,
p.intestazione AS author
FROM opera o
JOIN multi_rel m
ON m.tipoa = 'opera'
AND m.ida = o.id
LEFT JOIN persona p
ON o.autore = p.id
WHERE m.idb = '25'
AND m.tipob = 'formametrica'
UNION
SELECT o.id AS id,
o.tiposcheda AS type,
o.titolo AS title,
o.titoloperord AS ordered_title,
p.intestazione AS author
FROM opera o
JOIN rel r
ON r.tipoa = 'opera'
AND r.ida = o.id
LEFT JOIN persona p
ON o.autore = p.id
WHERE r.idb = '25'
AND r.tipob = 'formametrica'
ORDER BY author, ordered_title]: Got error 28 from storage engine