sql_query: select autore, left(autore,1) as autore_iniziale,id from (SELECT jmb_joodb_sample2.autore,jmb_joodb_sample2.id FROM jmb_joodb_sample2 where Pubblicato=1 ORDER BY RAND()) as sub WHERE autore is not null group by sub.autoresql_query: select autore, left(autore,1) as autore_iniziale,id from (SELECT jmb_joodb_sample2.autore,jmb_joodb_sample2.id FROM jmb_joodb_sample2 where Pubblicato=1 ORDER BY RAND()) as sub WHERE autore is not null group by sub.autore