Re: Can't use subselect in check constraint

> > Is this something that will change anytime soon?  I could not find
anything about it in the todo...
>
> My understanding is that check constraints can't be queries;  at least I
> have never seen them.

Considering that you could potentially have to reevaluate each CHECK
constraint every time you updated any table in the database, I would think
it would be a *real* bad idea to allow that. There is no way to
automatically create the triggers needed to satisfy "When should I check the
constraint?"

If it can't be constructed as a check against a literal value or values, or
a foreign key constraint, it should be up to the user to maintain that
consistency check with the appropriate triggers.

Greg