SELECT StuID FROM Participates_in INTERSECT SELECT StuID FROM Student WHERE age  <  20
Show the ids for all the students who participate in an activity and are under 20.
SELECT StuID FROM Participates_in INTERSECT SELECT StuID FROM Student WHERE age < 20
select stuid from participates_in intersect select stuid from student where age < value
Show the ids for all the students who participate in an activity and are under 20 .