CREATE TABLE volume (volume_id NUMBER, volume_issue CLOB, issue_date CLOB, weeks_on_top NUMBER, song CLOB, artist_id NUMBER)
CREATE TABLE artist (artist_id NUMBER, artist CLOB, age NUMBER, famous_title CLOB, famous_release_date CLOB)
CREATE TABLE music_festival (id NUMBER, music_festival CLOB, date_of_ceremony CLOB, category CLOB, volume NUMBER, result CLOB)

What are the categories of music festivals for which there have been more than 1 music festival?
SELECT category FROM music_festival GROUP BY category HAVING COUNT(*) > 1
SELECT "category" FROM "music_festival" GROUP BY "category" HAVING COUNT(*) > 1