Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE prereq (course_id VARCHAR); CREATE TABLE course (course_id VARCHAR)
### Question:
Find the id of the courses that do not have any prerequisite?
### Answer:
SELECT course_id FROM course EXCEPT SELECT course_id FROM prereq