CREATE TABLE Courses (course_name VARCHAR(255), course_id VARCHAR(255)); CREATE TABLE Student_Course_Enrolment (course_id VARCHAR(255))
What are the names of the courses that have exactly 1 student enrollment?
    
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