Show the theme for exhibitions with records of an attendance below 100
select t2.theme from exhibition_record as t1 join exhibition as t2 on t1.exhibition_id = t2.exhibition_id where t1.attendance < 100
Show the theme for exhibitions with records of an attendance above 500
select t2.theme from exhibition_record as t1 join exhibition as t2 on t1.exhibition_id = t2.exhibition_id where t1.attendance > 500
Show me the dates of those exhibitions
select t1.date from exhibition_record as t1 join exhibition as t2 on t1.exhibition_id = t2.exhibition_id where t1.attendance > 500