whats the course id of statistics
select course_id from courses where course_name = "statistics"
whats the course description of french
select course_description from courses where course_name = "French"
which course has most number of registered students ?
select t1.course_name from courses as t1 join student_course_registrations as t2 on t1.course_id = t2.course_id group by t1.course_id order by count ( * ) desc limit 1