'Twas brillig, and Chris at 12/12/08 01:20 did gyre and gimble:
Micah Gersten wrote:
Colin Guthrie wrote:
The ON DELETE CASCADE option is key here... "DELETE FROM students
where student_id=1" will remove all traces of that student from the
db... all the course they've attended, all the instructors who have
taught them etc. keeps things nice and tidy without having to put the
structure in your code all over the place.
Col
Why would you want to delete the instructors when deleting the student?
I think he meant the link between the student & instructor (in the
student_instructor table), not the instructor itself.
lol, indeed, that's what I meant... Sorry I thought it was implied in
the context!
Say you have the following layouts
instructors: instructor_id, name
students: student_id, name
instructor_students: instructor_id, student_id
This structure would hold a list of instructors and a list of studends
and also a one to many mapping of instructors to students.
If you delete a student the FK can cascade to the instructor_students
table and thus delete the records that indicate a given instructor (or
instructors) taught them.
Col
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