How many courses that do not have prerequisite?
CREATE TABLE prereq (course_id VARCHAR); CREATE TABLE course (course_id VARCHAR)
SELECT COUNT(*) FROM course WHERE NOT course_id IN (SELECT course_id FROM prereq)
### Context: CREATE TABLE prereq (course_id VARCHAR); CREATE TABLE course (course_id VARCHAR) ### Question: How many courses that do not have prerequisite? ### Answer: SELECT COUNT(*) FROM course WHERE NOT course_id IN (SELECT course_id FROM prereq)