err:SELECT id,img,num_ordine,nome,cognome,descr,descr_en,descr_breve,commento_en,descr_breve_en,commento,link1,link2,link3,commento_img,online FROM tblstudenti WHERE online=1 and id in (select idstudente from tblstudenti_corsi sc inner join tblcorsi c on c.id=sc.idcorso where c.idstrumento = (select id from tblstrumenti where codice='presenza-scenica')) order by cognome,nome