你得在rooms表中先添加一条room_id=20000的记录,然后
INSERT INTO classes(department, course, description, max_students,
current_students, num_credits, room_id)
VALUES ('HIS', 101, 'History 101', 30, 11, 4, 20000);
INSERT INTO classes(department, course, description, max_students,
current_students, num_credits, room_id)
VALUES ('HIS', 101, 'History 101', 30, 11, 4, 20000);
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