issues with regression data
- In the regression schema, there are several long chains of the form: grandparent->parent->child. Some of the child tables define an explicit FK to the grandparent while the others don't. For example, the following chains are similar:
department->course->prerequisite and department->course->class.
However only in the first chain, there's a direct FK from class to department; in the second chain, there's no FK from prerequisite to department. Is it by design or should be fixed?
Columns student.school and student.program are nullable, but there are no students that do not belong to some program.
Same issue with class.instructor.
The schema permits an instructor to have more than one appointment, but all instructors have either one or no appointments.
There are too few rows in the prerequisite table, in particular, there's no course that both //has// prerequisites and //is// a prerequisite.