Question: What are the names of the courses that have exactly 1 student enrollment?
Schema: create table courses (course_name varchar, course_id varchar, PRIMARY KEY (course_name)); create table student_course_enrolment (course_id varchar, PRIMARY KEY (course_id))
SQL: 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(*) = 1