Database: student_transcripts_tracking
Question: For each semester, what is the name and id of the one with the most students registered?
SQL: select t1.semester_name ,  t1.semester_id from semesters as t1 join student_enrolment as t2 on t1.semester_id  =  t2.semester_id group by t1.semester_id order by count(*) desc limit 1