I flipped a coin and ended up lucky. Two answers can both be considered correct.
No, a foreign key constraint can not be created across databases. If you refer to the actual constraint of that name, as supported by SQL Server.
Yes, a foreign key constraint can be enforced across databases using triggers. If you refer to the actual meaning of the constraint in a logical model.
With just the "yes" and "no" answers and a slight rewording of the question to prevent the ambiguity, this would have been a great question. With this wording *and* the presence of both "no" and "yes, with a trigger" in the answers, the question tries to trick people into giving the wrong answer. I assume that this was not the intention of the author - but it does have that effect!
Hugo Kornelis, SQL Server MVP
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