A constraint can only compare columns or values within the same row in the
same table.
If you need to compare a value with values located in other tables, you may
write a before insert/update triggers that compares the incoming value with
the allowed values and returns an error if the value does not match.

Mit freundlichen Grüßen / Best regards

Birgitta Hauser

"Shoot for the moon, even if you miss, you'll land among the stars." (Les
"If you think education is expensive, try ignorance." (Derek Bok)
"What is worse than training your staff and losing them? Not training them
and keeping them!"

-----Ursprüngliche Nachricht-----
Von: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] Im Auftrag von rpglist@xxxxxxxxxxx
Gesendet: Wednesday, 19.9 2012 23:27
An: midrange-l@xxxxxxxxxxxx
Betreff: Constraint based upon a separate file

I know how to add a typical check constraint where it ensures that the value
matches a short list of codes, etc. I have been searching for the past few
hours to no avail for an example that shows how to add a check constraint
based upon the value in a separate file:

Quick and dirty example would be a state field of two characters that has to
match a predfined table of state abbrev's or a zipcode lookup table...

Does anyone have any examples I can reference? I have been all over the
reference manual and so far haven't found what I'm looking for.



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