Question

Situation is this:
I have a table for staff and another one for course.
In course I will have a column called coordinator which will refer to the staff_id.
This is because some staff are coordinators and some are not, etc etc.

Staff_id is an IDENTITY hence it is auto-incrementing and I have to make sure the in the course table, it won’t follow this auto-increment.

I’m just unsure how do I implement the check constraint for this case.

Answer 1

If I’m understanding your requirements properly you can add a foreign key constraint to the table so that it references itself:

ALTER TABLE Staff 
ADD CONSTRAINT FK_Staff_Coordinator FOREIGN KEY (Coordinator)
REFERENCES Staff (StaffID)

ADENDUM

I think I had misunderstood your requirements, I missed the part about a course table. So now I am thinking that the course table needs to link back to the staff table, in which case the command would be:

ALTER TABLE Course
ADD CONSTRAINT FK_Course_Coordinator FOREIGN KEY (Coordinator)
REFERENCES Staff (StaffID)

You are of course free to implement your own naming convention for constraints.