SELECT country FROM singer WHERE age  >  40 INTERSECT SELECT country FROM singer WHERE age  <  30
Show countries where a singer above age 40 and a singer below 30 are from.
SELECT country FROM singer WHERE age > 40 INTERSECT SELECT country FROM singer WHERE age < 30
select country from singer where age > value intersect select country from singer where age < value
Show countries where a singer above age 40 and a singer below 30 are from .