How many students are enrolled in "AI"?
select count(*) from courses as t1 join student_course_enrolment as t2 on t1.course_id = t2.course_id where t1.course_name = "AI"
Tell me the names of the courses that have student enrollment bigger than 5.
select t1.course_name from courses as t1 join student_course_enrolment as t2 on t1.course_id = t2.course_id group by t1.course_name having count(*) > 2
What are the student ID and personal name of the student with at least two enrollments?
select t1.student_id, t2.personal_name from student_course_enrolment as t1 join students as t2 on t1.student_id = t2.student_id group by t1.student_id having count(*) >= 2