Thomas Kellerer <spam_eater(at)gmx(dot)net> writes:
> While I agree that this SQL should not have been written like this in the first place, I wonder why Postgres doesn't actively prevent this (like e.g. Oracle).
If Oracle does that, they're violating the SQL standard --- there is
nothing in the standard that supports rejecting an ALTER TABLE ADD
CONSTRAINT on the grounds that it's redundant. The spec only says
you can't give two constraints the same name.
regards, tom lane