Show the result of a set difference between tables Q and R
Here is what you looking at (Set Difference)


Q - R
Set Q Minus Set R


In MySQL

SELECT Q.*
FROM Q LEFT JOIN R USING (D, E)
WHERE R.E IS NULL;


Here is what the classmates are saying (Symmetric Difference)


(Q - R) U (R - Q) or (Set Q Minus Set R) Union (Set R Minus Set Q)
Also (Set Q Union Set R) Minus (Set Q Intersection Set R)


In MySQL

SELECT A.* FROM
(SELECT Q.* FROM Q LEFT JOIN R
USING (D, E) WHERE R.E IS NULL) A
UNION
SELECT B.* FROM
(SELECT R.* FROM R LEFT JOIN Q
USING (D, E) WHERE Q.E IS NULL) B;


Please go ask Your Teacher !!!