Courses Without Enrollments

Return the titles of courses that no student has enrolled in, ordered by title.

Table schema

Courses(id INT PRIMARY KEY, title VARCHAR(30))
Enrollments(student_id INT, course_id INT)

Sample data

Courses
id | title
1 | Algorithms
2 | Databases
3 | Compilers
4 | Networks

Enrollments
student_id | course_id
10 | 1
11 | 1
10 | 2
12 | 4