CREATE TABLE artist (artist_id NUMBER, name CLOB, country CLOB, year_join NUMBER, age NUMBER)
CREATE TABLE exhibition (exhibition_id NUMBER, year NUMBER, theme CLOB, artist_id NUMBER, ticket_price NUMBER)
CREATE TABLE exhibition_record (exhibition_id NUMBER, date CLOB, attendance NUMBER)

Which themes have had corresponding exhibitions that have had attendance both below 100 and above 500?
SELECT T2.theme FROM exhibition_record AS T1 JOIN exhibition AS T2 ON T1.exhibition_id = T2.exhibition_id WHERE T1.attendance < 100 INTERSECT SELECT T2.theme FROM exhibition_record AS T1 JOIN exhibition AS T2 ON T1.exhibition_id = T2.exhibition_id WHERE T1.attendance > 500
SELECT "T2"."theme" FROM "exhibition_record" "T1" JOIN "exhibition" "T2" ON "T1"."exhibition_id" = "T2"."exhibition_id" WHERE "T1"."attendance" < 100 INTERSECT SELECT "T2"."theme" FROM "exhibition_record" "T1" JOIN "exhibition" "T2" ON "T1"."exhibition_id" = "T2"."exhibition_id" WHERE "T1"."attendance" > 500