There are tables student and course. There are course_ids in student. Now replace course_ids with course_names.

   Select s.*, (
            Select wm_concat(c.name)
            From course c
            Where c.id in (
                    SELECT REGEXP_SUBSTR(s.course_ids, '[^,]+', 1, LEVEL, 'i') AS d_ids  
                    FROM DUAL  
                    CONNECT BY LEVEL <= LENGTH(s.course_ids) - LENGTH(REGEXP_REPLACE(s.course_ids, ',', ''))+1)
                    
                    )
            )
    From student s