Ошибка 1064 - ожидаемое поведение с неверным синтаксисом.
CREATE TABLE studentcourse
( sid INT NOT NULL COMMENT 'PK, FK ref student.sid'
, cid INT NOT NULL COMMENT 'PK, FK ref course.cid'
, grade DECIMAL(4,1)
, PRIMARY KEY (sid, cid)
, CONSTRAINT studentcourse_fk1 FOREIGN KEY (sid) REFERENCES student (sid)
ON UPDATE CASCADE ON DELETE RESTRICT
, CONSTRAINT studentcourse_fk2 FOREIGN KEY (id) REFERENCES course (cid)
ON UPDATE CASCADE ON DELETE RESTRICT
)