Database: e_learning
Question: What are the student ID and login name of the student who are enrolled in the most courses?
SQL:
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