Database: theme_gallery
Question: Show all artist names with an average exhibition attendance over 200.
SQL: select t3.name from exhibition_record as t1 join exhibition as t2 on t1.exhibition_id  =  t2.exhibition_id join artist as t3 on t3.artist_id  =  t2.artist_id group by t3.artist_id having avg(t1.attendance)  >  200