All but one of the following queries produces the same results.
Which one produces a different result or produces an error?
A.
SELECT * FROM class JOIN student ON class.class_id=student.class_id
B.
SELECT * FROM class INNER JOIN student ON class.class_id=student.class_id
C.
SELECT * FROM class LEFT JOIN student ON class.class_id=student.class_id D
SELECT * FROM class JOIN student ON class.class id=student.class id
D.
SELECT * FROM class INNER JOIN student ON class.class_id=student.class_id WHERE NOT ISNULL(student.class_id)
E.
SELECT * FROM class LEFT JOIN student ON class.class_id=student.class_id WHERE NOT ISNULL(student.class id)
Explanation:
C will also return mismatches, ie it will return class_id (1st table) though not matched to a student_id (2nd table)
— D and E are also outer joins but the WHERE NOT ISNULL clause removes them from the output.