Table schema:
CREATE TABLE Student_Enrolment (semester_id VARCHAR); CREATE TABLE Semesters (semester_name VARCHAR, semester_id VARCHAR)

Question: What is the semester which most student registered in? Show both the name and the id.
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