Jan Wieck wrote:
>
> Any combination of attributes in a table referenced to by one
> or more FOREIGN KEY ... REFERENCES constraint of another
> table shall have a UNIQUE and NOT NULL constraint.
...
> So we assume here that any PK is unique and cannot contain NULL's.
What is the reasoning behind requiring this ?
I can't see anything that would mandate this - * NULLs are'nt equal anyway and ar even disregarded under your
currentdescription. Or are you just protecting yourself against the case where the foreign key field is set to
null- could this be handled the same as deleting for cascaded constraints ? * UNIQUE would save us the check for
existingother possible referenced values - is this mandated by SQL spec ?
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Hannu
