3.22

Rewrite the WHERE clause

WHERE UNIQUE (SELECT title FROM course)

without using the UNIQUE construct.

---

One method

WHERE 1 >= ALL (
    SELECT COUNT(*)
    FROM course
    GROUP BY title
)

Another method

WHERE NOT EXISTS (
    SELECT * 
    FROM course AS c1, course AS c2
    WHERE c1.course_id != c2.course_id AND c1.title = c2.title
)