On Tuesday, July 13, 2021, David Gauthier <davegauthierpg(at)gmail(dot)com> wrote:
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> I suppose I could write a stored procedure to do this and call it in a
> check constraint. But I was wondering if there is something more elegant.
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You cannot use a check constraint here as the behavior is not immutable.
You can use a trigger function though. Or normalize the table and use the
built-it foreign key triggers.
David J.