Question: Show the years in which orchestras that have given more than one performance are founded.
Schema: create table performance (orchestra_id varchar, PRIMARY KEY (orchestra_id)); create table orchestra (orchestra_id varchar, PRIMARY KEY (orchestra_id))
SQL: select year_of_founded from orchestra as t1 join performance as t2 on t1.orchestra_id = t2.orchestra_id group by t2.orchestra_id having count(*) > 1