WordPress database error: [Subquery returns more than 1 row]
SELECT B.nom as obra, B.IDelement2 as IDE2, B.t1 as tobra, A.nom as artista, C.nom as pais FROM Relacions R INNER JOIN elements A ON A.IDelement2=R.ID2 INNER JOIN elements B ON B.IDelement2=R.ID1 INNER JOIN Relacions V ON R.ID2=V.ID1 INNER JOIN elements C ON C.IDelement2=V.ID2 WHERE R.relacio="és obra de" AND R.ID1 IN (SELECT Relacions.ID1 FROM Relacions WHERE Relacions.relacio="pertany" AND Relacions.ID2=(SELECT elements.IDelement2 FROM elements WHERE elements.nom="Altres" AND elements.sistema="Museu")) AND V.relacio="pertany" ORDER BY A.nom