CREATE TABLE students (student_id NUMBER, date_of_registration TIME, date_of_latest_logon TIME, login_name CLOB, password CLOB, personal_name CLOB, middle_name CLOB, family_name CLOB)
CREATE TABLE subjects (subject_id NUMBER, subject_name CLOB)
CREATE TABLE student_course_enrolment (registration_id NUMBER, student_id NUMBER, course_id NUMBER, date_of_enrolment TIME, date_of_completion TIME)
CREATE TABLE courses (course_id NUMBER, author_id NUMBER, subject_id NUMBER, course_name CLOB, course_description CLOB)
CREATE TABLE student_tests_taken (registration_id NUMBER, date_test_taken TIME, test_result CLOB)
CREATE TABLE course_authors_and_tutors (author_id NUMBER, author_tutor_atb CLOB, login_name CLOB, password CLOB, personal_name CLOB, middle_name CLOB, family_name CLOB, gender_mf CLOB, address_line_1 CLOB)

What are the student ID and login name of the student who are enrolled in the most courses?
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
SELECT "T1"."student_id", "T2"."login_name" FROM "student_course_enrolment" "T1" JOIN "students" "T2" ON "T1"."student_id" = "T2"."student_id" GROUP BY "T1"."student_id" ORDER BY COUNT(*) DESC FETCH FIRST 1 ROWS ONLY