Question: What are the dates of enrollment and completion for each of those students? Please list it in the table.
SQL: SELECT T1.date_of_enrolment, T1.date_of_completion FROM Student_Course_Enrolment AS T1 JOIN Students AS T2 ON T1.student_id   =   T2.student_id GROUP BY T1.student_id HAVING COUNT ( * )   < =   2