I need to give administrators the ability of adding instructors to an instructor pool. Instructors will be assigned to courses from the pool. Multiple instructors can be assigned to the same course. I'm trying to decide if I would be better off handling one table or two tables. If I use one table then I will need to check to see if the instructor has been assigned to a course, if so, add another entry otherwise update the courseid column. If I use two tables then I will need to check the pool table to make sure an instructor exists before making an entry in the instuctor table. I'm leaning towards one table. What do you think is best? Thank you for your help.

I'm guessing from your description that the situation you are trying to model has instructors, courses, and course assignments. That looks like three tables to me.

Presumably there are attributes which are constant for any given instructor, demographic data like their name, qualifications, date of hire, whether they are currently active and available for assignment, etc. These attributes are independant of any assignment of the instructor, so should be in a separate table which defines these constants.

The same can be said for any given course. The course description, location, meeting times, etc, are constant attributes of the course and are independant of any instructor assignment.

Finally, there is the assignment of a given instructor to a given course. Perhaps you need to keep a history of what instructors were assigned to what courses when. Such information would not be available if you only had a current assignment value in the instructors table.

It all depends on your application's information requirements, but it looks to me like the three tables I describe may be appropriate, but only you know for sure.

Jeff Mason
Custom Apps, Inc.
www.custom-apps.com