Calculate the percentage of high-level undergraduate course.
high-level undergraduate course refers to courseLevel = 'Level_400'; percentage = divide(count(course.course_id) when courseLevel = 'Level_400', count(course.course_id)) * 100%
SELECT CAST(SUM(CASE  WHEN courseLevel = 'Level_400' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(*) AS per FROM course