Question

I’m trying to model optional self dependence in mySQL wherein for instance a course may have one or more prerequisite(s) which are other courses in the same table.

Answer 1

Have a separate table which lists the course’s prerequisites:

create table class_prerequisite (
   classID int not null,
   prerequisiteClass int not null,
   required bit not null default false,
   primary key (classID, prerequisiteClass)
);

where classID and prerequisiteClass are foreign keys pointing back at your classes table. The ‘required’ field would signal if it’s a mandatory or optional prereq.