Context: CREATE TABLE Student_Course_Enrolment (student_id VARCHAR); CREATE TABLE Students (login_name VARCHAR, student_id VARCHAR)
Question: Find the student ID and login name of the student with the most course enrollments
Answer: SELECT T1.student_id, T2.login_name FROM Student_Course_Enrolment AS T1 JOIN Students AS T2 ON T1.student_id = T2.student_id GROUP BY T1.student_id ORDER BY COUNT(*) DESC LIMIT 1