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cheerios · 02-03-2004, 04:48 PM

ok can't help you on the first one, but the second one I can.

here's the deal. a PK has to be unique for each entry, right? so with the primary key of Students being sid and the PK of Enrolled being BOTH sid and courseID, then both sid & courseID have to match to cause a key constraint.

so you could have
sid_______CourseID
9887--------1235
9887--------1236
both in enrolled and not cause an error. theo only time you'd have problems is if the same student tried to enrol in the same course multiple times. am i making sense?

02-03-2004, 04:48 PM	#2 (permalink)
cheerios Banned Location: 'bout 2 feet from my iMac	ok can't help you on the first one, but the second one I can. here's the deal. a PK has to be unique for each entry, right? so with the primary key of Students being sid and the PK of Enrolled being BOTH sid and courseID, then both sid & courseID have to match to cause a key constraint. so you could have sid_______CourseID 9887--------1235 9887--------1236 both in enrolled and not cause an error. theo only time you'd have problems is if the same student tried to enrol in the same course multiple times. am i making sense?