Context: CREATE TABLE Courses (course_name VARCHAR, course_id VARCHAR); CREATE TABLE Student_Course_Enrolment (course_id VARCHAR)
Question: What are the names of the courses that have exactly 1 student enrollment?
Answer: 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